It turns out sapphire is a very useful high-tech material, due to its hardness, insulating properties, optical transparency, and thermal conductivity. By starting with a tiny seed crystal, a huge column of highly pure crystal can be slowly drawn out of a molten vat, producing big honking specimens like the one here. The color of sapphire is produced by impurities - this very pure example is colorless.

Seen at the Nikon booth at Photonics West 2015

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