November 2020 Outcrop

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

Volume 69 • No. 11 • November 2020

OUTCROP | November 2020

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Vol. 69, No. 11 | www.rmag.org

OUTCROP The Rocky Mountain Association of Geologists

1999 Broadway • Suite 730 • Denver, CO 80202 • 800-970-7624 The Rocky Mountain Association of Geologists (RMAG) is a nonprofit organization whose purposes are to promote interest in geology and allied sciences and their practical application, to foster scientific research and to encourage fellowship and cooperation among its members. The Outcrop is a monthly publication of the RMAG.

2020 OFFICERS AND BOARD OF DIRECTORS PRESIDENT

2nd VICE PRESIDENT-ELECT

Jane Estes-Jackson janeestesjackson@gmail.com

Peter Kubik pkubik@mallardexploration.com

PRESIDENT-ELECT

SECRETARY

Cat Campbell ccampbell@caminoresources.com

Jessica Davey jessica.davey@sproule.com

1st VICE PRESIDENT

TREASURER

Ben Burke bburke@hpres.com

Chris Eisinger chris.eisinger@state.co.us

1st VICE PRESIDENT-ELECT

TREASURER ELECT

Nathan Rogers nathantrogers@gmail.com

Rebecca Johnson Scrable rebecca.johnson@bpx.com

2nd VICE PRESIDENT

COUNSELOR

Dan Bassett dbassett@sm-energy.com

Donna Anderson danderso@rmi.net

RMAG STAFF DIRECTOR OF OPERATIONS

Kathy Mitchell-Garton kmitchellgarton@rmag.org DIRECTOR OF MEMBER SERVICES

Debby Watkins dwatkins@rmag.org CO-EDITORS

Courtney Beck clbeck14@gmail.com Nate LaFontaine nlafontaine@sm-energy.com Wylie Walker wylie.walker@gmail.com DESIGN/LAYOUT

Nate Silva nate@nate-silva.com

ADVERTISING INFORMATION

Rates and sizes can be found on page 35. Advertising rates apply to either black and white or color ads. Submit color ads in RGB color to be compatible with web format. Borders are recommended for advertisements that comprise less than one half page. Digital files must be PC compatible submitted in png, jpg, tif, pdf or eps formats at a minimum of 300 dpi. If you have any questions, please call the RMAG office at 800-970-7624.

Ad copy, signed contract and payment must be received before advertising insertion. Contact the RMAG office for details.

DEADLINES: Ad submissions are the 1st of every month for the following month’s publication.

WEDNESDAY NOON LUNCHEON RESERVATIONS

RMAG Office: 800-970-7624 Fax: 323-352-0046 staff@rmag.org or www.rmag.org

The Outcrop is a monthly publication of the Rocky Mountain Association of Geologists

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Outcrop | November 2020 OUTCROP

RMAG/RPS Short Course IntroductIon to FluId SaturatIonS and ProPertIeS In unconventIonal ‘Shale’ reServoIrS with Andy Pepper

11 05 20 email: staff@rmag.org | phone: 800.970.7624 OUTCROP | November 2020

1999 Broadway, Suite 730, Denver CO 80202

This course, run by The Rocky Mountain Association of Geologists in partnership with RPS, provides a solid introduction to the ‘geochemical petrophysics’ of ‘Shale’ reservoirs.

This course is designed for Geoscientists, including Petrophysicists, and Engineers seeking an up-todate understanding of the physics and chemistry that determine performance of these difficult reservoirs.

$200/RMAG members $235/Nonmembers Register at www.rmag.org 4

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Vol. 69, No. 11 | www.rmag.org

follow: @rmagdenver

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

CONTENTS FEATURES

DEPARTMENTS

12 Lead Story: A Brief History of Notable Colorado Seismicity & Seismic Stations

6 RMAG October 2020 Board of Directors Meeting

28 Mineral Of The Quarter: Cuprite

8 President’s Letter 22 Online Lunch Talk: Alex Zumberge

ASSOCIATION NEWS

26 Online Lunch Talk: Dr. Tyler Lyson & Dr. Ian Miller

2 RMAG Summit Sponsors

27 Welcome New RMAG Members!

4 RMAG/RPS Short Course on Fluid Saturation

27 In The Pipeline

COVER PHOTO

35 Outcrop Advertising Rates

‘The Sheep Mountain Tunnel Mill, commonly called the Crystal Mill was built in 1893. A waterwheel powered an air compressor for drill bits and ventilation in nearby Sheep Mountain, Inez, and Bear Mountain silver mines. Today it is regarded as a Colorado icon, and one of the most photographed sites in the state.’

Image captured by Stephen Sturm, Oct 5 2020.

7 MiT Webinar Series: Upcoming Events 9 RMAG Data Science webinar series

36 Advertiser Index 36 Calendar

11 Stories in Stone — RMAG Virtual Field Trip 24 Publish with The Mountain Geologist

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RMAG OCT. 2020 BOARD OF DIRECTORS MEETING

By Jessica Davey, Secretary jessica.davey@sproule.com

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on compiling the 2021 budget. Debby and Kathy have been maintaining the RMAG office virtually.

Debby and Kathy reported that the Geohike Challenge was a success. We had participants across the country, and some fantastic geology and creative photos shared in the competition.

The Continuing Education Committee has hosted 17 online events since we went virtual, and they have all went very well! This past month alone, the Unconscious Bias two-day course, the monthly luncheon talk, and the Practical Python course all took place with great attendance numbers. The Membership Committee wrapped up the Geohike Challenge, and are busy planning upcoming events, so keep an eye out on the RMAG website. The Publications Committee reports they have lead articles set for the Outcrop through January 2021 and through July 2021 for the Mountain Geologist, so get ready for some inspiring reading! The On the Rocks Committee is hosting a virtual field trip run by David Williams called “Stories in Stone,” see the RMAG website to register.

The Educational Outreach Committee will have a presence to promote RMAG at the Colorado Science Conference, which will be held online on November 14.

Are any of you dressing up in geo-themed costumes this year?

My daughter and I have been spending a lot of time coming up with a fun costume idea. I think we’ve settled on being cave bats.

During my online idea search, I found this gem.

I may have to buy one to wear year-round!

Happy Halloween, fellow rock lovers! I’m compiling this writeup on a cold, snowy morning, watching our Halloween decorations getting covered up with snow in the front yard. I hope you are all staying warm and dry as we get into the (hopefully) snowy time of year here in Colorado!

The RMAG Board of Directors met virtually at 4 pm on Wednesday, October 21. Everyone was present except for Nathan Rogers and Jessica Davey. Ben Burke graciously stepped in to take notes for the meeting since I was not able to attend. Treasurer, Chris Eisinger, and Treasurer-Elect, Rebecca Johnson Scrable, report that the RMAG financials are still looking good despite the struggle with COVID this year and are working

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Webinar Series 2020 Members in Transition

Rocky Mountain Members in Transition (MiT) is a joint effort of members of AAPG, SPE, WOGA, COGA, DWLS, and RMAG in the Rocky Mountain region to help association members in the midst of a career transition.

Webinars are free and open to all

All times 12pm-1pm MST except where noted

Register at www.rmag.org

November 5, 2020, 4pm-5pm

Dr. Christine Economides, Texas A&M University  Net Zero Carbon Opportunity: Can We Lead This Transition?

November 11, 2020

Speaker Panel: Patrick Rutty (Enverus), Ridvan Akkurt (Schlumberger), & Stephanie Perry (GeoMark)  Making the Leap: From Operating Company to Service Company Employment (or the reverse)

November 19, 2020

Speaker Panel: Stephen Zaiss (Merrill Lynch), Francisco Blanch (Bank of America) and Joshua Tracy (Merrill Lynch)  Tectonic Shifts: Navigating Changes in the Energy Sector Visit our partner website Petroleum Pivoters!

Rockies MiT Members in Transition

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PRESIDENT’S LETTER

By Jane Estes-Jackson

Family Tradition

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on the basis of a negative gravity anomaly from a torsion balance survey that was confirmed by reflection seismograph. As such, it was the first field in Louisiana discovered through the use of geophysics. The original interpretation was that the gravity low was due to an underlying salt dome, as that was the dominant play type of that time. After drilling it was determined that the dome was actually a rollover anticline on the downthrown block of a growth fault. So it was also the first growth-fault-trapped field discovered in Louisiana, and kicked off a new play looking for similar “Tepetate-type structures” throughout the Gulf Coast. In 1938 the North Tepetate Field was discovered by Atlantic Refining (later Atlantic Richfield) on the upthrown side of the fault. In the early 1950’s, Anchor Gasoline Corp., a subsidiary of Phillips Petroleum Company, opened a small plant there that made gasoline, propane, and butane from the wells operated by Atlantic Richfield. My grandfather was

One of my cousins got bored during the quarantine earlier this year, and used that downtime to digitize all of the family pictures that she had found while cleaning out her parents’ house. Many of these photos, which were stuffed into a box that was hidden in a closet, were old and without much identification. She shared them with the rest of the family as she scanned them, and we all became amateur detectives trying to figure out who and what some of them portrayed.

One particular group of photos really resonated with me. When I was a very small child my grandfather ran a small gas plant at the North Tepetate Field in rural Louisiana, and some of my earliest memories are of visiting him and my grandmother there. They lived in a small house on the property, and my grandfather’s commute consisted of a short walk to the plant’s office.

The Tepetate Field (named after the company that generated the original prospect) was discovered in 1935 by Continental Oil Company

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R ocky M ountain a ssociation of G eoloGists

t uesdays o ctobeR 13 thRouGh

n oveMbeR 17

Data Science

WEBINAR SERIES 2020

Now Virtual!

The RMAG presents “Digital Workflows in Oil & Gas�

RMAG has pivoted! We have transformed the content of the Data Science Symposium we had planned for April into a series of hour-long online sessions taking place over the course of 6 weeks.

Each webinar will feature either two talks or one talk and a networking/discussion session. See all the details at www.rmag.org.

Data analytics is more important than ever. Join us to explore this vital topic!

Register for individual sessions or the whole series at www.rmag.org Price: Individual session: $20 member/$25 non-member; Series: $75 member, $110 nonmember (includes RMAG membership) email: staff@rmag.org | phone: 800.970.7624 Vol. 69, No. 11 | www.rmag.org

1999 Broadway, Suite 730, Denver CO 80202

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PRESIDENT’S LETTER

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the superintendent of that plant from the time it opened until it closed in 1971, when he took an early retirement.

Pop was a very hardworking and humble individual. His family moved around a lot while he was growing up, mostly following the railroad. As a young man he got a job hauling drill pipe with a mule team and a wagon in the oil fields around Seminole, Oklahoma during the 1920’s boom in that area. He married my grandmother in 1934 and by the time my dad and his brothers were born in the mid 1930’s he was working at the Phillips refinery in Oklahoma City. They later moved to Borger, Texas so he could work in the Phillips refinery there. In the 1940’s he transferred to Anchor and worked at their gas plants in Salem, Illinois and Pine Prairie, Louisiana before ending up at North Tepetate.

But I learned most of this after he died. He wasn’t, like much of his generation, comfortable talking about himself. My dad and my uncle didn’t talk about it much either and they are gone now too.

Going through those old pictures and reconstructing his career let me see him in a whole new light, and made me realize how much we have in common. I like to think I inherited his work ethic, along with his sense of humor. But it also struck me that we both worked in the oil business (albeit at opposite ends), and we both spent most of our careers working for one company, and I find myself wishing that I could talk to him about it. He helped make me who I am, and I am very proud to share his name.

Well Log Digitizing • Petrophysics Petra® Projects • Mud Log Evaluation Bill Donovan

Geologist • Petroleum Engineer • PE

(720) 351-7470 donovan@petroleum-eng.com OUTCROP | November 2020

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RMAG VIRTUAL FIELD TRIP NOVEMBER 11 | 4PM

PRESENTED BY

D AV I D WILLIAMS AUTHOR - SPEAKER VIRTUAL FIELD TRIP LEADER

ONLINE - FREE & OPEN TO ALL REGISTER AT WWW.RMAG.ORG In this virtual exploration of building stone from across the United States and Italy, author David Williams discusses history, transportation, and architecture to give you a new way to appreciate urban geology. Plus, we’ll even “visit” a couple of quarries and see where the stone originates.

email: staff@rmag.org | phone: 800.970.7624 Vol. 69, No. 11 | www.rmag.org

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LEAD STORY

By Kyren Bogolub

A Brief History of

NOTABLE COLORADO SEISMICITY & Seismic Stations

ISTOCK

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olorado’s largest known historical earthquake occurred on November 7th 1882. At the time of this earthquake, Colorado’s population was around 200,000 and its largest cities barely had 4,000 people (Kirkham and Rogers, 1986). Therefore, the reports of the earthquake being felt by people (known as “felt reports”) in various documents are sparse and unevenly distributed geographically across the state. Due to a lack of seismometers at the time, these felt reports are all we have to pin down the location, time of occurrence, and approximate magnitude of this historical earthquake, which has been a challenge. Estimates of these parameters are generally made by careful evaluation of historical records such as newspaper articles, government documents, and other archives maintained for historical purposes.

Analyzing these felt reports requires not only a good deal of assessment of each source’s reliability, but also a methodology for converting qualitative observations, such as plaster falling off a wall, into quantitative estimates of distance from the epicenter, and magnitude of the earthquake. One common method for doing this is by using the Modified Mercalli

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Intensity Scale. This scale assigns a value for “severity of ground shaking” to a location based on the various effects of the shaking on the landscapes, structures, or people. For example, an intensity of VIII or “severe” is assigned to an area if damage is great to poorly built structures and heavy furniture has been overturned.

An intensity of IV or “light” applies to an area if the shaking is felt by many indoors, but few outdoors; dishes, windows and doors are disturbed. Assigning these intensities to historical records can be tricky since there are often unanswerable questions such as whether the person who felt the event was indoors or outdoors, or if a particular building that experienced damage was well built.

Once the intensities are assigned on the basis of historical records, the data points are contoured using the estimated intensity values. These contours, called isoseismals or isoseismal lines, create a sort of bullseye around the area of maximum intensity which can help narrow down the possible epicenter location. Local geology and known fault systems can further refine estimates of the epicenter location and magnitude. The isoseismal map for the 1882

C

FIGURE 1: Isoseismal map for the 1882 Colorado earthquake from Kirkham and Rogers (1986)

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Table 1

Colorado’s largest historic earthquakes from Colorado Geological Survey Publication MI-95

Date

Location

1870, Dec. 4 1871, Oct. 1880, Sep. 17 1882, Nov. 7 1891, Dec. 1901, Nov. 15 1913, Nov. 11 1944, Sep. 9 1955, Aug. 3 1960, Oct. 11 1966, Jan. 4 1966, Jan. 23 1967, Aug. 9 1967, Nov. 27 2011, Aug. 22

Pueblo/Ft. Reynolds Lily Park, Moffat Co Aspen North-Central CO Maybell Buena Vista Ridgeway area Montrose/Basalt Lake City Montrose/Ridgway N. E. of Denver CO-NM border near Dulce, NM N. E. of Denver N. E. of Denver Trinidad

earthquake from Kirkham and Rogers (1986) is shown in Figure 1. Researchers typically compare isoseismal maps of pre-instrumental earthquakes to similar maps for modern earthquakes, for which the epicentral location, depth, and magnitudes are better known because of instrument recordings. Kirkham and Rogers (1986) concluded the 1882 earthquake probably occurred within the area where aftershocks were felt (stippled area in Figure 1). Spence et al. (1996) compared the felt effects of Colorado’s 1882 earthquake to Wyoming’s more recent 1984 Laramie Mountains earthquake. They concurred with Kirkham and Rogers’ epicentral location for the 1882 earthquake, and increased the estimated moment magnitude to 6.6.

Several other historical earthquakes are documented in Colorado (Table 1), with one of the largest being a 5.5 in 1960 (Talley and Cloud, 1962). This event was also assigned a location and magnitude using felt reports and the Modified Mercalli Intensity Scale to create an isoseismal map by Tally and Cloud (1962).

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— — — 6.6 — — — — — 5.5 5 5.5 5.3 5.2 5.3

Intensity VI VI VI VII VI VI VI VI VI V V VII VII VI VII

The arrival of seismographs in Colorado greatly improved our understanding of its seismicity. The first seismometer in Colorado was installed in 1909 at Regis University (at the time Regis College) in Denver and operated until 1988 (Udias and Stauder, 1996) when the Regis College Seismological Observatory ceased operations. This was the only station in the state until 1954 when the University of Colorado at Boulder installed a seismograph that operated until 1959 (Healy et al., 1968). In 1961, the Colorado School of Mines installed a station named GOL in Bergen Park near Evergreen Colorado.

A few months later in March of 1962, the Chemical Corps of the US Army began injecting waste water into a disposal well at Rocky Mountain Arsenal (RMA) (Evans, 1966). In April of 1962 a magnitude 1.5 earthquake occurred near Denver marking the beginning of a series of earthquakes, commonly known as The Denver Earthquakes (Figure 2). The Denver Earthquakes consisted of over 1000 events in the 1960’s including a magnitude a 5.3 on August 9th 1967. In 1966, David

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Magnitude

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LEAD STORY of controlling seismicity through fluid injection. Researchers selected the Rangely Oil Field in northwestern Colorado and northeastern Utah as a desirable location for this experiment because it was known to experience induced earthquakes, the geology was well studied, and the fluid pressure could be measured and controlled. In the experiment, researchers deployed an array of seismometers to record seismic activity in the oil field and then reduced the fluid pressure of the subsurface by backflowing injection wells. After concluding that the decrease in pressure correlated with a decrease in seismicity, they again increased the pressure to verify that fluid pressure can trigger earthquakes. This was a robust and significant conclusion; however, they also determined that induced earthquakes tend to occur on preexisting faults. This conclusion is intuitive, but also suggests a complicated relationship between fluid injection location and earthquake location.

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M. Evans published a paper demonstrating a spatial and temporal correlation between the monthly rate of waste water injected at RMA and the monthly rate of earthquake occurrences in the Denver area. The original plot from his paper summarizing the temporal correlation is shown in Figure 3. This correlation demonstrated one of the earliest known cases of human-induced seismicity. Although it was only briefly installed, the University of Colorado at Boulder seismic station along with the Regis station were important for validating the induced seismicity hypothesis because it demonstrated a lack of seismicity in the area prior to onset of wastewater injection (Healy et al., 1966).

The identification of induced seismicity at RMA inspired decades of research projects and experiments. One of the most significant was the Rangely Oil Field experiment (Raleigh et al., 1976). In this experiment, researchers attempted to test the feasibility

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FIGURE 2: Map of Colorado seismicity from USGS catalog, 1960-2020. Highlighted areas show regions discussed in the text.

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LEAD STORY largest releases of seismic energy in Colorado during modern times (Bott and Wong, 1995). At less than 10km spacing, this dense coverage of stations allowed for more accurate events locations, magnitudes as well as focal mechanisms. Focal mechanisms indicate the orientation of the fault and direction of slip that the earthquake occurred on. The earthquakes locations defined a northwest-striking and northeast-dipping fault plane which was consistent with many of the focal mechanisms in the swarm (Bott and Wong, 1995). The focal mechanisms also suggested that the events occurred on normal faults, leading researchers to conclude that crust in this region is subjected to

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The 1980’s and 1990’s saw the installation of several local seismic networks in Colorado and increased the capacity of researchers to publish seismicity catalogs. However, these networks were mostly targeting specific geographic regions and statewide coverage was still lacking (Sheehan, 2000). Still, these new networks enabled the study of a few notable earthquakes including the 1986 Crested Butte earthquake swarm (Figure 2). This series of about 200 earthquakes was partially recorded by an array of portable seismometers deployed by the U.S. Geological Survey (USGS) to monitor the swarm, which collectively was one of the

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FIGURE 3: Plot from Evans (1966) showing the number of earthquakes per month recorded in the Denver

area and the monthly volume of contaminated wastewater injected into the Rocky Mountain Arsenal well.

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FIGURE 4:

Map of Transportable Array station locations color coded by installation year.

Map courtesy of USArray.

an extensional stress regime. Apart from these instrument-recorded earthquakes, historical records also suggest that this region has a relatively high rate of seismicity (Kirkham and Rogers, 2000).

One of the notable seismic networks installed beginning in the 1980s was the Paradox Valley Seismic Network (PVSN). This network is owned and operated by the U.S. Bureau of Reclamation as part of the Paradox Valley Unit project. This project was a result of the U.S. Colorado River Basin Salinity Control Act of 1974 which was passed to help reduce the salinity of the Colorado River by preventing briny ground water from entering the river. This is accomplished by extracting the ground water and then reinjecting it 4.7 km underground in one of the deepest waste water wells in the world (Kharaka et al., 1997). Because of earlier studies on induced seismicity, the PVSN was installed several years prior to the onset of injection beginning in 1985 and has continued to operate in some configuration to this day. As predicted, induced earthquakes occurred as a result of the wastewater injection (Figure 2), notably a magnitude 3.9 in 2013 and a magnitude 4.5 in 2019 (USGS 2020). While the data is not publicly available, the stations of the PVSN have been used by the USGS to locate both local and global earthquakes.

A new window into Colorado seismicity arrived in 2004, when the EarthScope Transportable Array (TA)

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began making its way across the United States. This was an array of transportable seismometers that was designed to monitor a swath of land with instruments at a spacing of about 70 km for a period of two years before moving east to the next swath. Figure 4 shows the progression of the TA stations across the contemporaneous US. The TA stations occupied Colorado primarily from 2007-2010. From 2008-2009 the density of stations was further increased by the Colorado Rocky Mountain Experiment and Seismic Transects known as the CREST array. These stations provided unprecedented statewide seismic station coverage of Colorado. Seismicity studies from these two arrays provided a much more complete picture of statewide seismicity patterns.

Nakai et al. (2017a, b) used these two arrays to create a comprehensive catalog of Colorado seismicity from 2008-2010. The analysis of this catalog formed the basis of two papers, the first of which largely focused on the seismicity of the Rio Grande Rift (Nakai et al., 2017a). In this study, they found higher seismicity rates in northwestern Colorado than previously observed and used these seismicity patterns to confirm that the Rio Grande Rift extends into north-central Colorado. These patterns suggest that the extensional tectonic regimes inferred from earlier earthquake studies (such as the Crested Butte studies) are related

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LEAD STORY

to this broad impact from extension of the northern Rio Grande Rift (Nakai et al., 2017a). Nakai et al. confirmed previous observations that seismicity in Colorado tends to manifest in localized swarms. A recent example of this is an east-west-trending swarm of small earthquakes (Figure 2) from late 2018 to 2019 located south and southeast of Great Sand Dunes National Park (Bell, 2020). The largest event of this Sand Dunes swarm was a magnitude 3.4 in February of 2019 (USGS, 2020).

The second paper focused on the seismicity of the Raton Basin in southern Colorado and northern New Mexico (Nakai et al., 2017b). This was the most seismically active area in the state of Colorado during the 2008-2010 study period (Figure 2). It is believed that most earthquakes in the Raton Basin are induced by wastewater injection, again due to a temporal correlation between injection rates and seismicity rates (Nakai et al., 2017b). In addition to the seismicity analysis, Nakai et al. (2017b) also used pore pressure modeling to show that the local geology and preexisting faults can cause fluid migration from the injection depth into deeper basement rocks causing induced earthquakes even at great distances from the injection location.

The current Colorado Geological Survey Seismic Network (CGSSN) began as four TA stations that were adopted by the Colorado Geological Survey (CGS) in 2010. The University of Colorado, Colorado State University and Colorado College all helped support CGS’s adoption efforts. Of all the TA stations that formally occupied Colorado, these sites were selected based on proximity to the Front Range, where most of Colorado’s population is concentrated, and data quality. Landowner permission was also a factor since the original TA agreements with station hosts were based on two year deployments only.

CGS formally named the CGSSSN in 2016 when they installed their first seismic station near Briggsdale in Weld County. This station was installed because a magnitude 3.2 induced earthquake shook the city of Greeley in 2014. This station also helped support a temporary regional network (with network code XU) deployed by Anne Sheehan and the University of Colorado. The XU network was used to study various aspects of induced seismicity including mitigation strategies (Yeck et al., 2016). Since its deployment, the XU

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network has been used to locate over 1200 small magnitude earthquakes from 2014-2019 most of which are in the vicinity of the Greeley Airport (Figure 2).

Since 2018, CGS has installed 4 more stations near Hayden, Lamar, Estes Park, and Greeley (station at Briggsdale was relocated to Greeley), these stations and others are shown on the map in Figure 5. The CGS stations are used to more precisely locate earthquakes not only in Colorado but all over the globe. CGS staff collaborate with many universities and colleges in Colorado including Colorado School of Mines, University of Colorado-Boulder, Colorado State University and Colorado Mountain College. These collaborations often help with gaining land access, providing students to assist with station installation and analyzing data. Over the next two years, CGS plans to install an additional four stations along the Front Range and central Colorado.

A typical set up for a CGSSN seismic station is shown in Figure 6. The seismic sensor is buried underground and a cable is run underground to the tower which hosts the solar panel, cellular antenna, GPS antenna, and a box with other needed equipment. The tower is located 15-20 feet from the sensor in order to reduce noise on the seismic records from the motion of the tower caused by wind. Figure 7 shows inside the equipment box which houses the battery, the charge controller, the cellular modem and the all-important digitizer/data logger. The digitizer takes the analog electronic signal from the sensor and converts it to digital counts which is then saved to a hard disk and telemetered to the USGS National Earthquake Information Center via cellular antenna.

Colorado has a long history of both natural and induced earthquakes, some of which have caused significant damage to buildings and infrastructure. Colorado is at a distance from active plate boundaries so its seismicity is unique, providing an opportunity to study as of yet poorly understood intraplate tectonics and the effects and mechanics of human induced earthquakes.

Future seismic monitoring by CGS and others will help understand the geology and tectonics of our state as well as better assess the hazard and risks that this tectonic environment poses.

It is to the credit of William “Pat” Rogers that we have as much knowledge of Colorado Quaternary tectonics and earthquake hazards as we do. Pat Rogers

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FIGURE 5:

Map of longterm deployment seismic stations in Colorado. C0 is network code for stations operated by Colorado Geological Survey Seismic Network. N4 is the Central and Eastern U.S. Network.

US is the United States National Seismic Network.

Colorado Earthquake Hazard Mitigation Council, 2013, Colorado Earthquake Hazards: Colorado Geological Survey Publication MI-95, 1 p.

Evans, D.M., 1966, The Denver Area Earthquakes and The Rocky Mountain Arsenal Disposal Well: The Mountain Geologist, v. 3, p. 23–36.

Healy, J.H., Jackson, W.H. and Van Schaack, J.R, 1966, Microseismicity studies at the site of the Denver earthquakes, Geophysical and geological investigations relating to earthquakes in the Denver area, Colorado: U.S. Geological Survey Open-File Report 66-60, 56 p.

Healy, J.H., Rubey, W.W., Griggs, D.T. and Raleigh, C.B., 1968, The Denver Earthquakes: Science, v. 161, p.

1301–1310.

Kharaka, Y.K, Ambats, G., and Thirdsen, J.J., 1997, Deep well injection of brine from Paradox Valley, Colorado: Potential major precipitation problems remediated by nanofiltration: Water Resources Research, v.

33, p. 1013-1020.

Kirkham, R.M., and Rogers, W.P., 1986, An interpretation of the November 7, 1882 Colorado earthquake: Colorado Geological Survey Open File Report 86-8, 39 p.

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was the former Chief of the Engineering an Environmental Section at the Colorado Geological Survey for decades and the interim Colorado State Geologist after John Rold retired and Vicki Cowart was appointed to the position. Pat spearheaded research into Quaternary faulting, paleoseismicity, and earthquake history. In addition to blazing trails in science, he was known for his love of the outdoors and volunteered many hours building and restoring hiking trails in Colorado. Pat Rogers passed away on September 5th, 2020. He will be missed and remembered by those who knew him and appreciated for the scientific legacy he left. On behalf of the Colorado Geologic Survey, I humbly say thank you, and good bye.

REFERENCES

Bell, J., 2020, Seismic Activity in the Northern Sangre de Cristo Fault Zone: Master’s thesis, University of Colorado, Boulder Colorado, 60 p.

Bott, J. and Wong, I.G., 1995, The 1986 Crested-Butte Earthquake Swarm and Its Implications for Seismogenesis in Colorado: Bulletin of the Seismological Society of America, v. 85, p. 1495–1500.

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FIGURE 6:

Installation of LAMA near Lamar Colorado.

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FIGURE 7:

Equipment stored on tower at seismic station LAMA.

Front Colorado (1882) and Wyoming (1984): Bulletin of the Seismological Society of America v. 86, p.

1804–1819.

Talley, H.C., and Cloud, W.K, 1962, United States Earthquakes, 1960: U.S. Geological Survey Open-File Report 84-960, 95 p.

Udias, A. & Stauder, W., 1996, The Jesuit Contribution to Seismology: Seismological Research Letters, v. 67, p. 10–19.

US Geological Survey, 2020, USGS Earthquake Catalog.

Yeck, W.L., Sheehan, A.F., Benz, H.M., Weingarten, M. and Nakai, J., 2016, Rapid Response, Monitoring, and Mitigation of Induced Seismicity near Greeley, Colorado: Seismological Research Letters, v. 87, p.

837–847.

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Kirkham, R.M., and Rogers, W.P., 2000, Colorado Earthquake Information, 1867-1996: Colorado Geological Survey Bulletin 52, 161 p.

Nakai, J.S., Sheehan, A.F. and Bilek, S.L., 2017a, Seismicity of the Rocky Mountains and Rio Grande Rift from the EarthScope Transportable Array and CREST temporary seismic networks, 2008-2010: Journal of Geophysical Research, v. 10, p. 31–20.

Nakai, J.S., Weingarten, M., Sheehan, A.F., Bilek, S.L. and Ge, S., 2017b, A Possible Causative Mechanism of Raton Basin, New Mexico and Colorado Earthquakes Using Recent Seismicity Patterns and Pore Pressure Modeling: Journal of Geophysical Research, v. 122, p. 8051–8065.

Raleigh, C.B., Healy, J.H. and Bredehoeft, J.D., 1976, An Experiment in Earthquake Control at Rangely, Colorado: Science, v. 191, p. 1230–1237.

Sheehan, A.F., 2000, Microearthquake Study of the Colorado Front Range: Combing Research and Teaching in Seismology: Seismological Research Letters, v. 71, p. 175–179.

Spence, W., Langer, C.J. and Choy, G.L., 1984, Rare, Large Earthquakes at the Laramide Deformation

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KYREN BOGOLUB is responsible for maintaining the Colorado Geological Survey Seismic Network. Kyren is also a Ph.D. candidate in Geophysics at the University of Colorado, Boulder.

Aside from Colorado seismicity, Kyren is also interested in western United States tectonics, in particular the formation of the Rocky Mountains.

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ONLINE LUNCH TALK

FREE!

Speaker: Alex Zumberge Nov. 4, 2020 | 12:00 pm - 1:00 pm

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Geochemical Correlation of Late Mississippian-Sourced Crude Oils from the Western USA

By John B. Curtis, John E. Zumberge and J. Alex Zumberge; GeoMark Research, Houston TX

ALEX ZUMBERGE has extensive lab experience in oil and rock extract analyses with emphasis on correlation tools like bulk organic properties, lipid biomarkers and carbon isotopes. He has over eight years’ experience in a lab environment doing experiments himself as well as overseeing general sample/project flow

OUTCROP | November 2020

these type-area outcrop units of Central Montana to the sub-surface of the Williston Basin of western North Dakota (Bottjer et al., 2019). The Heath-sourced oils in the Williston are strikingly different than those of Central Montana. Although they both have PZE, Williston Heath/Amsden oils lack the evaporitic signatures seen in the Heath/Amsden oils of Central Montana, have very low sterane to hopane ratios (i.e., low algae/bacteria relative abundances), and most surprisingly, have extremely high C28/C29 regular sterane ratios. Prasinophytes are a unique class of green algae that produce C28 sterols as major steroid constituents and thrive in oxygen depleted environments that are unfavorable for other planktonic primary producers (Schwark and Empt 2006). High C28/C29 sterane values have only been measured in oils from Late Cretaceous

Some twenty-five million years after the deposition of the renowned Late Devonian/Early Mississippian black shales across North America, Middle to Late Mississippian sediments also generated oils in western North America. These areas include Central Montana, western North Dakota in the Williston Basin, the Las Animas Arch area of eastern Colorado, the Arkoma, Ft. Worth and Permian basins of Oklahoma and Texas, as well as Railroad Valley of Nevada and the Thrust Belt in Central Utah. Using sterane and terpane biomarkers and carbon isotopes, these Mississippian-sourced oils indicate a wide range of source rock depositional environments. The Heath Formation of Central Montana generated oils with evaporitic/carbonate biomarker features including both photic zone euxinia (PZE) and stratified water column indications.

However, workers have been challenged to correlate

» CONTINUED ON PAGE 24

through each analysis phase. Alex recently finished his PhD in Organic Geochemistry at the University of California – Riverside where he specialized on sterane/hopane relationships through time from the Precambrian to the present. Additionally, Alex has experience with traditional analytical techniques (LC, GC, GC-MS,

22

GC-MS/MS) as well as new analytical approaches that allow access to the kerogen-bound biomarker pool within rock extracts via Hydrogen Pyrolysis, HyPy. Currently, Alex is the Director of Analytical Services at GeoMark Research and manages oil technical service projects as well as the new GRI+ rock lab.

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ONLINE LUNCH TALK Arch oils are the only pre-Cretaceous sourced oils we are aware that have these exceptionally high C28 steranes (C28/C29 > 1.5), and likely reflect a dominance of Prasinophyte algae in oxygen depleted waters. The Mississippian Barnett (TX), Caney (OK), and Chainman (NV) shale sourced oils are generally correlative with each other amid some variation in degree of upwelling and algal/bacteria sources. All have typically low Paleozoic C28/C29 sterane ratios (<1). The Covenant oil from the central Utah Thrust Belt correlates best with the carbonate facies oils from Central Montana.

» CONTINUED FROM PAGE 22

to Miocene source rocks (reflecting the evolutionary rise of the diatoms), except for Late Mississippian reservoired oils on the Las Animas Arch. In fact, the Late Mississippian Las Animas Arch oils, likely sourced from Late Mississippian shales (perhaps from the Hugoton Embayment to the east in Kansas), also correlate best with the Williston Heath/Amsden oils with respect to the classic pristane/phytane ratio, carbon isotopic compositions, and lack of upwelling biomarkers. The Late Mississippian Williston and Las Animas

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Rise of the Mammals: Exceptional Continental Record of Biotic Recovery after the Cretaceous– Paleogene Mass Extinction

By Dr. Tyler Lyson & Dr. Ian Miller

DR. TYLER LYSON is curator of vertebrate paleontology at the Denver Museum of Nature & Science, where he is responsible for the fossil reptile collection.

His research focuses on the early origin and evolution of reptiles, particularly turtles, as well as the driver(s) and tempo of the Cretaceous-Paleogene mass extinction and subsequent ecosystem recovery. He is working on projects in the Denver Basin in Colorado, Williston Basin in North Dakota and Montana, and Karoo Basin in South Africa. Lyson received his Ph.D. and M.A. in geology and paleontology from Yale University, and his B.A. from Swarthmore College. Lyson

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record. An extraordinary new discovery east of

Sixty-six million years ago a 6-mile-wide asteroid slammed into Earth and caused the extinction of more than 75% of life on Earth, including the dinosaurs. This was the single worst day for life on Earth. How and when life rebounded in the aftermath of the extinction has been shrouded in mystery due to a poor fossil

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was a postdoctoral researcher at the Smithsonian National Museum of Natural History before joining the Denver Museum in 2014.

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Rockies and along the Colorado Front Range, the Grand Staircase Escalante National Monument in Utah, the San Juan Basin in New Mexico, the Williston Basin in North Dakota, and the Morondova Basin in Madagascar. Beyond his work as a scientist, Ian has led Museum initiatives aimed at deepening people’s connection with the natural world, and unearthing major trends in new and existing audiences that will define the future of Museums. Ian received his PhD and MA in geology and paleobotany from Yale University, and his BA from The Colorado College. He has been with the museum since 2006.

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MINERAL OF THE QUARTER

By Ronald L. Parker Senior Geologist, Senior Geologist, Borehole Image Specialists, P. O. Box 221724, Denver CO 80222 | ron@bhigeo.com

CUPRITE The Mineral Glowing Ember

» CONTINUED ON PAGE 29

BELOW: Translucent blood-red cuprite displaying vitreous luster, octahedral form and internal reflection. Katanga (Shaba) Province, Democratic Republic of the Congo. Used with permission from John Betts Fine Minerals, Inc.

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MINERAL OF THE QUARTER: CUPRITE hydrocuprite, octahedral copper, oxydulated copper, red glassy copper ore, ruby copper and ruberite, most of which have fallen out of favor (Mindat, 2020). Cuprite has been noted as a common corrosion by-product on smelted copper (Korzhavyi and Johansson, 2011). It is a bit of inorganic irony that cuprite has been found as a secondary mineral growing on ancient human-crafted copper and bronze artifacts (Dana, 1922, p. 411).

Cuprite has a specific gravity of 6.1 and a hardness of ~3.5 to 4. Cuprite, like fluorite, has cleavage along {111} yielding 4 cleavage planes. Unlike fluorite, however, cleavage in cuprite is poor and “interrupted” – so cleavage faces are not often observed (Mineral Data Publishing, 2005). Cuprite, though soft, is brittle, which is reflected in conchoidal to uneven fracture. Cuprite crystallizes in the hexoctahedral (4/m, bar3, 2/m) cubic crystal class. Euhedral crystals are a common occurrence and are often highly symmetric, displaying cubes, octahedrons and dodecahedrons, frequently

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Cuprite, cuprous (Cu ) oxide (Cu2O), is a common mineral in the oxidized zone of copper-bearing ore deposits and is a minor, though important, source of copper. Cuprite belongs to the isometric (cubic) crystal system and is commonly seen as well-formed cubic, octahedral and dodecahedral crystals, often as intergrown crystalline masses. An acicular variety, chalcotrichite, appears as felted masses of tiny red fibers.

Although it is too soft for jewelry, the display of bright red internal reflections – like a glowing ember – makes this mineral a favorite of collectors. Cuprite is the first substance recognized as a semiconductor and was, therefore, an important material in the evolution of modern electronics.

Cuprite was named in 1845 by Wilhelm Karl von Haidinger for its copper content. The word copper, of course, comes from the Roman name for the island of Cyprus, which was among the most significant sources of copper to the Mediterranean world (Chaline, 2012; Still, 2016). Cuprite has other monikers, including: +

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Bright, distorted octahedral cuprite crystals displaying a submetallic luster. In spite of the metallic sheen, these crystals exhibit a distinctive red translucent color when illuminated from behind. Near the city of Rubtzovsk, Altai Krai region, Siberia, Russia. When 1st discovered, these crystals were found “floating” in pockets of red or white clay attended by beautiful dendritic copper crystals (Levitskiy, 2009). Used wth permission from John Betts Fine Minerals.

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Lustrous, red-black octahedral cuprite crystals parked atop native copper and calcite rhombohedra. These cuprites are small, up to 2 mm across. From Wheal Jewel, Crofthandy, Cornwall, England. Used with permission from John Betts Fine Minerals, Inc.

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MINERAL OF THE QUARTER: CUPRITE

» CONTINUED FROM PAGE 29

as combined forms (Klein, 2002). Crystal aggregates and penetration twins are also a frequent occurrence (Cook, 2001). Cuprite also occurs in a massive or an earthy habit as well as hairlike crystals (chalcotrichite).

Cuprite is differentiated from similar minerals (like cinnabar or hematite) by higher symmetry as shown by crystal forms, a distinctive brownish-red, sparkly streak and differences in hardness (Klein, 2002). Cuprite is softer than hematite or sphalerite and harder than cinnabar, chalcopyrite or copper (Johnsen, 2002).

Cuprite exhibits only small variation from stoichiometric Cu2O: isomorphic substitution of other cations appears to be uncommon (Klein, 2002). The mineral is 88% copper, which gives it the highest Cu yield of any copper ore (Other than elemental copper, of course).

Cuprite appears in a variety of red-colored shades that can mimic red-colored gems. The carmine red of some translucent cuprite specimens is known as “ruby-copper” (Bonewitz, 2013). The dark red of many cuprite samples can sometimes appear to be almost black. Cuprite appears to change color due to extended exposure to light, slowly darkening from red to dark gray (Bonewitz, 2005). Cuprite has an adamantine (brilliant) to sub-metallic luster.

Cuprite displays one remarkable property that makes it a favorite of mineral enthusiasts: a tendency to glow a bright crimson-red when subjected to high-intensity transmitted light. This astonishing characteristic is the result of internal reflection inside the crystal. I was gobsmacked when I first witnessed a metallic looking octahedral chunk of cuprite transmogrify into a flaming scarlet ember under a small, but powerful, flashlight beam. If you haven’t seen this behavior in cuprite, you should put it on your bucket list. I decided to illustrate this glow for my article, yet found myself without a cuprite specimen. Luckily, at the time I was preparing this article, the 2020 Denver Gem and Mineral Show was running. Conducting “fieldwork” at the show, (with requisite facial mask and social distancing due to COVID-19), I discovered that cuprite was hard to find. Luckily, my quest was fulfilled

by Rocky Krichbaum, proprietor of Rocky Houndenstein, LLC, who was in possession of some stellar cuprites from the Milpillas Mine in Sonora, Mexico. Rocky

Dark-red mass of octahedral cuprite crystals with chrysocolla and quartz. From the Katanga (Shaba) Province, Democratic Republic of the Congo. 28 mm across. Used wth permission from John Betts Fine Minerals.

Large malachite pseudomorph after cuprite with matrix inclusions. Chessy-les-Mines, Rhone-Alpes (NW of Lyons), France. Used with permission from John Betts Fine Minerals.

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showed me several excellent cuprites (two of which I now possess). He graciously allowed me to photograph one eye-popping specimen and then he called forth the “scarlet fire” from the same sample with a bright flashlight. (The last 2 photographs in this article are from that encounter). Although I’ve not seen a detailed explanation for the intensity of the internal reflections, I’ll wager that this optical feature relates to the very high refractive index of cuprite (2.849), which is considerably higher than that of diamond (2.42) (Nesse, 2002).

Cuprite has a very distinctive appearance in thin section, characterized by a very high positive relief and red, orange-yellow or lemon-yellow color (Mineral Data Publishing, 2005). In reflected light, cuprite appears gray-blue with deep-red internal reflections that are diagnostic (Nesse, 2002). Although cuprite is isometric, it nevertheless is well-known to exhibit an unusual optical anisotropy with pale bluish-gray

Malachite pseudomorph of an octahedral cuprite crystal from Chessy-les-Mines, Rhone-Alpes, France. Photo by Albert S. Wylie.

» CONTINUED ON PAGE 32

Felted mass of finely acicular chalcotrichite whiskers. From the Ray Mine, Mineral Creek District, Pinal County, Arizona. This locality was the source of the natural material studied

by Veblen and Post (1983). Photo used with permission from John Betts Fine Minerals.

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MINERAL OF THE QUARTER: CUPRITE

An aggregate mass of cuprite crystals from the Milpillas Mine, Cuitaca, Santa Cruz, Sonora, Mexico. This specimen was for sale by Rocky Houndenstein, LLC at the 2020 Denver Gem and Mineral Show. Proprietor Rocky Krichbaum demonstrated the internal reflection-driven “scarlet fire” effect using this sample (next picture). Photo by Ronald L. Parker.

A large dark red cuprite crystal coated by a rind of fibrous green malachite microcrystals. From the Onganja Mine, Seeis, Khomas, Namibia. Used with permission from John Betts Fine Minerals.

to olive-green polarization colors. Libowitzky (1994) demonstrated that the apparent optical anisotropy is an artifact of thin-section preparation – specifically, mechanical alteration from surface polishing with diamond abrasives. A change in polishing materials and procedures was shown to retain isometric optical behavior.

Chalcotrichite is the fibrous variety of cuprite. It is composed of delicate, single-crystal hairs or whiskers of cuprite that grow with extreme aspect ratios (of 1000:1 or more) in reticulated, tufted or matted aggregates (Mineral Data Publishing, 2005). To explore fibrous cuprite, Veblen and Post (1983), studied synthetic chalcotrichite whiskers and natural specimens from the Ray Mine, Pinal County, Arizona, using transmission electron microscopy (TEM). (Note that the chalcotrichite photo in my article is from the Ray Mine).

Veblen and Post identified that the most common fiber morphology (one with a with a square cross-section) is the result of propagation of a single screw-dislocation

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along one of the a-crystallographic axes.

Cuprite is formed by the interaction of near-surface, oxygen-bearing ground water with reduced, sulfidic, copper-bearing igneous intrusives. Supergene processes oxidize the primary sulfidic copper ores to create the suite of secondary minerals that are so beloved of mineral collectors, the oxides and carbonates (Cook, 2001). Cuprite is associated with many other minerals common to copper-ore deposits including native copper, malachite, azurite, chrysocolla, calcite, bronchianite, antlerite, atacamite, tenorite and iron oxides and clay minerals (Mineral Data Publishing, 2005).

Although cuprite is prized, it is not fit for jewelry.

As Bonewitz (2013) observes, “Faceted stones are too soft to wear, but their exceptional brilliance and garnet-red color make them highly desirable as collector’s stones.” (p. 58). One element of this appeal is that large cuprite crystals – of a size that engenders faceting - are vanishingly rare. Most faceted cuprite crystals were collected from the unique discovery of large, gemmy

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» CONTINUED ON PAGE 33

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MINERAL OF THE QUARTER: CUPRITE

cuprite crystals from Onganja, Seeis, Namibia, which has reported crystals up to 6 inches across and up to 2 kg in mass (Arem, 1977). This amazing discovery has since been mined out. Joel Arem, former curator of the Smithsonian National Gem and Mineral Collection, elaborates, “…faceted cuprite… is considered one of the most collectible and spectacular gems in existence, with its deep garnet coloring and higher brilliance than a diamond. Only the gem’s soft nature prevents it from being among the most valuable jewelry stones.” (Wikipedia, 2020a).

Cuprite is a special mineral with special properties.

Synthetic cuprous oxide is the earliest material demonstrated to have semiconductor properties. Rectifier diodes based on cuprous oxide have been in use since the 1920s. Cuprite has a foundational place in the history of the modern semiconductor industry. Cuprous oxide has been extensively investigated as a potential low-cost material for solar cells (Musa, 1998) and is now being studied as a photocatalyst for producing

hydrogen from water. “New applications of Cu2O in nanotechnology, spintronics and photovoltaics are emerging” (Korzhavyi and Johansson, 2011, p.4). In addition to these high-tech applications, cuprous oxide is used industrially as a pigment, as a fungicide and as an anti-fouling agent in marine paints (Wikipedia, 2020b).

Important localities for cuprite include: Tsumeb and Emke regions of Namibia; the Ural Mountains and the Altai Krai region of Russia; Chessy, France; Cornwall, England; Sonora, Mexico, and Broken Hill, NSW, Australia. In the United States, cuprite occurrences are significant in Santa Rita, New Mexico and the Bisbee, Clifton, Morenci and Ray mines in Arizona.

Cuprite! A magical burning ember of a mineral.

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ON-LINE REFERENCES

• https://www.minerals.net/mineral/cuprite.aspx • https://en.wikipedia.org/wiki/Cuprite • https://en.wikipedia.org/wiki/Copper(I)_oxide • https://www.mindat.org/min-1172.html

» CONTINUED ON PAGE 34

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• http://www.handbookofmineralogy.org/pdfs/cuprite.pdf • http://webmineral.com/data/Cuprite.shtml#.X2GeNmhKiHs • http://copperoxides.altervista. org/ • https://meanings.crystalsandjewelry.com/cuprite/ • https://www.youtube.com/ watch?v=DVJzk6-J3MY (Excellent video describing space group symmetry of cuprite) • https://www.facebook.com/ collectorsedgeminerals/videos/1786845958289807 (Movie clip displaying internal reflection from a backlit cuprite specimen).

REFERENCES

Arem, Joel, 1977, Color Encyclopedia of Gemstones, Second Edition, New York: Van Nostrand Reinhold Company, 328 pp.

Bonewitz, Ronald Louis, 2005, Rock and Mineral: The Definitive Guide to Rocks, Minerals, Gems and Fossils, New York, New York: Dorling-Kindersley Limited, 360 pp. _______________, 2013, Smithsonian Nature Guide: Gems, New York, New York: Dorling-Kindersley Limited, 224 pp.

Chaline, Eric, 2012, Copper, in Fifty Minerals that Changed the Course of History, Buffalo, New York: Firefly Books, Inc., pp. 12-15.

Cook, Robert B., 2001, Cuprite: Mashamba West Mine, Shaba, Democratic Republic of Congo, and Red Dome Mine, Queensland, Australia, Rocks & Minerals, 76:248-251.

Dana, Edward Salisbury and

» CONTINUED ON PAGE 35

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William E. Ford, 1922, A Textbook of Mineralogy, Third Edition, New York, John Wiley & Sons, Inc., 720 pp.

Johnsen, Ole, 2002, Minerals of the World: Princeton University Press, Princeton, N.J. 439 pp.

Korzhavyi, P.A. and B. Johansson, 2011, Literature Review on the Properties of Cuprous Oxide Cu2O and the Process of Copper Oxidation, Swedish Nuclear Fuel and Waste Management Co. SKB TR-11-08, 47pp. Available on-line at https://inis. iaea.org/collection/NCLCollectionStore/_Public/43/041/43041487.pdf?r=1 Levitskiy, Victor, 2009, A New Find of Copper and Cuprite Crystals in Russia, Rocks and Minerals, 84:324-5.

Libowitzky, Eugen, 1994, Optical Anisotropy of Cuprite Caused by Polishing, The Canadian Mineralogist, 32: 353-358.

Mineral Data Publishing, 2005, Cuprite, http:// www.handbookofmineralogy.org/pdfs/cuprite.pdf Accessed 8/28/2020.

Musa, A. O., T. Akomolafe and M. J. Carter, 1998, Production of Cuprous Oxide, a Solar Cell Material,

by Thermal Oxidation and a Study of Its Physical and Electrical Properties, Solar Energy Materials and Solar Cells, 51: 305-316.

Nesse, William D., 2004, Introduction to Optical Mineralogy, 3rd Edition: New York: Oxford University Press, 348 pp.

Still, Ben, 2016, Copper: Relatively Reactive Redhead in The Secret Life of the Periodic Table: Unlocking the Mysteries of all 118 Elements, Buffalo, New York: Firefly Books, Inc., p.68-9.

Veblen, David R. and Jeffrey E. Post, 1983, A TEM Study of Fibrous Cuprite (Chalcotrichite): Microstructures and Growth Mechanisms, American Mineralogist, 68:790-803.

Wikipedia, 2020a, Cuprite, https://en.wikipedia.org/ wiki/Cuprite, accessed 8/28/2020.

Wikipedia, 2020b, Copper(I) Oxide, https:// en.wikipedia.org/wiki/Copper(I)_oxide, accessed 9/17/2020.

» CONTINUED FROM PAGE 34

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Vol. 69, No. 11 | www.rmag.org