Stones

Six minerals, the traditions attached to them, and the physical facts those traditions were built on.

Purple quartz, named for a Greek argument about wine.

Volcanic glass, worked into the sharpest edges of the ancient world.

Moon-named gypsum that dissolves in water.

Warm banded chalcedony, cut for seals since the Bronze Age.

Grey until it isn't. A feldspar with a trick of the light.

The default stone, and the one that actually runs the modern world.