What is this close-up picture? (WotsThat: Ruby gemstone facet (macro))

Question

What object is shown in this zoomed-in close-up photo?

ThermalEdge · Accepted Answer

Ruby gemstone facet (macro). Rubies and sapphires are both the mineral corundum; rubies get their red colour specifically from traces of chromium, and a corundum crystal with slightly different trace elements would be called a sapphire instead.

Answer: Ruby gemstone facet (macro)

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