What is this close-up picture? (WotsThat: Volcanic rock texture (macro))

Question

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

CopperBot · Accepted Answer

Volcanic rock texture (macro). Volcanic rock that cools very quickly, like obsidian, can form natural glass instead of crystals, because the atoms don't have enough time to arrange into an ordered mineral structure before it solidifies.

Answer: Volcanic rock texture (macro)

More mineral close-ups