CHEMISTRY
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diamond, the hardest substance known, save for a human heart grown cold. What spells the difference here, between carbon as ductile lubricant, a material you can spritz into balky locks, and carbon by De Beers? In graphite, each carbon atom is covalently bonded to three other carbon atoms, all of them lying in the same two-dimensional plane; there is no upstairs-downstairs blending of electrons but only the wan charms of van der Waals holding one floor to the next, so they slip-slide away. In a diamond, by contrast, the bonds are fully fleshed out in every direction. Now, each carbon is strapped covalently to four of its kind, the maximum possible, and across three-dimensional space. To the left, right, crownward, groundward; wherever a carbon looks, there's a carbon bound to it. They're packed together so tightly and with such crystalline homogeneity that light finds very little impediment to its passage, very few imperfections to bounce off of and muddy the view, and the diamond gleams translucently. And because anywhere one might want to slice, one encounters thickets of jealous carbon-carbon bonds, a diamond feels like forever; to cut a diamond, a professional diamond cutter uses another diamond. This painstaking compaction and positioning of carbon atoms is extremely difficult to accomplish. Getting every atom just where it needs to be to bond in a sororal three-dimensional mosaic, millions upon millions of flawlessly arrayed rings of four-faceted tetrahedrons, takes time and tremendous force. Until recently, the only place diamond factories could be found was hundreds of kilometers underground, in the Earth's mantle, where carbon stores subjected to great heat and pressure over millions or billions of years finally locked together in fixed constructs. Every so often, a volcanic eruption would spew a geyser of these diamonds to the surface, and another monarch might have his diadem, or Marilyn a pear-shaped friend. Industry also came to rely on diamonds for their unequaled ability to abrade metal machine parts into shape, and semiconductor manufacturers sought diamond bits to install in their microchips, to help prevent the embedded circuits from overheating. Diamonds happen to be excellent heat sinks, which is why even a room-temperature gem will feel cool to the touch. Put your fingertips or puckered lips against a diamond, and the jewel drains warmth from you to it, a heat transfer that your brain interprets as a brush with something cold; in fact, their high thermal conductivity, rather than their crystal clarity, earned diamonds the alias "ice." Whatever the argot, diamonds clearly were too useful to leave to chance delivery through a magma pipeline. In the mid-twentieth cen-