Judging quality
Look for a sharp, symmetrical cross with clean contrast against the body color. Polished slices are usually cut from the same crystal, so patterns run in families.
Silicate
Chiastolite
Andalusite grown with graphite inclusions arranged in a dark cross that appears when the crystal is sliced across. Every cross is slightly different, and the best show four crisp arms with no smearing.
Care
Hard and stable. Water and cloth.
History & lore
Known in Spain as the piedra de la cruz and carried by travellers on the Camino for centuries.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Chiastolite
- What is Chiastolite?
- Andalusite grown with graphite inclusions arranged in a dark cross that appears when the crystal is sliced across. Every cross is slightly different, and the best show four crisp arms with no smearing.
- How hard is Chiastolite and what is it made of?
- Chiastolite is a Silicate-family mineral with the composition Al2SiO5 with carbon. It crystallizes in the orthorhombic system and rates 6.5-7.5 on the Mohs hardness scale. It occurs in brown, black, tan.
- Where does Chiastolite come from?
- Notable localities for Chiastolite include China, Spain, Chile, California, USA.
- How do you tell good Chiastolite from filler?
- Look for a sharp, symmetrical cross with clean contrast against the body color. Polished slices are usually cut from the same crystal, so patterns run in families.
- How do you care for Chiastolite?
- Hard and stable. Water and cloth.
See it in person
Photographs only go so far
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.