Crystallography Of Gold

A Beautiful Element In All Of It’s Countless Forms And Shapes

Gold is a unique substance with extraordinary properties. An element, a mineral and a metal, gold occurs in nature alloyed commonly with silver but also with palladium, mercury, and copper. Its crystal structure is close-packed, face-centered cubic – imagine an atom of gold at each corner of a cube and in the middle of each face. Using up 74% of the space, this is one of the most efficient ways for spheres to pack together. Gold shares its face-centered cubic crystal structure with copper, nickel, platinum, and lead.

The crystallography, metallography, and composition of gold directly inform its remarkable properties – how it reacts to pressure, temperature, and fluids, and even its color. Quantum chemistry tells us that gold’s electrons move so rapidly that they shift the wavelength of absorbed light to blue and reflect the opposite color: lustrous metallic yellow. Gold’s other properties include resistance to corrosion, electrical conductivity, and malleability. Gold is quite soft – one gram of gold can be flattened into a one-meter square sheet! It keeps astronauts cool and protected from the sun and looks fancy on French desserts.

Because it’s so soft, gold can collect and form nuggets in fluvial beds and even be absorbed by trees. Though gold nuggets as big as several feet in diameter have been discovered, single crystals are quite rare and small. Native gold crystals usually form skeletal rounded octahedrons, cubes, and dodecahedrons. Sometimes they are elongated in specific crystallographic directions forming herringbone or dendritic twins. Others maybe flattened with octahedral, cubic, or triangular faces.

Large trapezohedron crystal (Side A)

Rob Bergmann

Large trapezohedron crystal

Rob Bergmann

Elongated skeletal dodecahedron with small rounded dodecahedron crystal

Rob Bergmann

Cubic crystals with skeletal cubic form

Rob Bergmann

Large trapezohedron crystal

Rob Bergmann

Large trapezohedron crystal (Side B)

Rob Bergmann

Truth, like gold, is to be obtained not by its growth, but by washing away from it all that is not gold.

- Leo Tolstoy, War and Peace

More Crystallography Resources:

For more about gold's classification, physical properties, chemical properties, and a database of remarkable specimens from across the world - check out the Mineral Database online: www.mindat.org