Judging quality
Naturally rounded with a slightly frosted skin; tumbled pieces are glossy all over. Genuine nodules are translucent when back-lit.
Volcanic glass
Rounded nodules of obsidian weathered free from the white perlite that once enclosed them. Held to a light they glow smoky translucent brown at the edges.

Naturally rounded with a slightly frosted skin; tumbled pieces are glossy all over. Genuine nodules are translucent when back-lit.
Glass. Keep from harder stones.
The name comes from an Arizona legend of Apache women mourning warriors at Big Picacho; the story is widely repeated and of uncertain age.
Cultural history, recorded as tradition rather than as medical or scientific claim.
See it in person
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.