Judging quality
The projection effect only works on slabs cut across the fibres. Satin spar selenite has a similar silk but does not transmit an image.
Borate
Ulexite
'TV rock' — parallel fibres act as natural optical fibres and project an image from the base of a cut slab to its polished top, so text under the stone appears to float on its surface.
Care
Water-soluble. Never wash it — a wet cloth will pit the surface permanently. Dry dusting only.
History & lore
Ulexite from the California desert has been mined at Boron since the twenty-mule-team borax era of the 1880s.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Ulexite
- What is Ulexite?
- 'TV rock' — parallel fibres act as natural optical fibres and project an image from the base of a cut slab to its polished top, so text under the stone appears to float on its surface.
- How hard is Ulexite and what is it made of?
- Ulexite is a Borate-family mineral with the composition NaCaB5O6(OH)6·5H2O. It crystallizes in the triclinic system and rates 2-2.5 on the Mohs hardness scale. It occurs in white, colorless, cream.
- Where does Ulexite come from?
- Notable localities for Ulexite include Boron, California, USA, Chile (Atacama), Kazakhstan, Argentina.
- How do you tell good Ulexite from filler?
- The projection effect only works on slabs cut across the fibres. Satin spar selenite has a similar silk but does not transmit an image.
- How do you care for Ulexite?
- Water-soluble. Never wash it — a wet cloth will pit the surface permanently. Dry dusting only.
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.