Eucryptite
| Eucryptite | ||
|---|---|---|
Mohs scale hardness 6.5 | | |
| Luster | Vitreous | |
| Streak | White | |
| Diaphaneity | Transparent to translucent | |
| Density | 2.67 | |
| Optical properties | Uniaxial (+) | |
| Refractive index | nω = 1.570 – 1.573 nε = 1.583 – 1.587 | |
| Birefringence | δ = 0.013 | |
| Other characteristics | Fluoresces pink to red or orange under SW UV | |
| References | [2][3][4] | |
Eucryptite is a
trigonal – rhombohedral crystal system. It typically occurs as granular to massive in form and may pseudomorphically replace spodumene. It has a brittle to conchoidal fracture and indistinct cleavage. It is transparent to translucent and varies from colorless to white to brown. It has a Mohs hardness of 6.5 and a specific gravity of 2.67. Optically it is uniaxial positive with refractive index
values of nω = 1.570 – 1.573 and nε = 1.583 – 1.587.
Its typical occurrence is in lithium-rich pegmatites in association with albite, spodumene, petalite, amblygonite, lepidolite and quartz.[3]
It occurs as a secondary alteration product of spodumene. It was first described in 1880 for an occurrence at its type locality, Branchville, Connecticut.[2] Its name was from the Greek for well concealed, for its typical occurrence embedded in albite.[2][3]
References
- S2CID 235729616.
- ^ a b c Mindat.org
- ^ a b c Handbook of Mineralogy
- ^ Webmineral data
 | This article about a specific silicate mineral is a stub. You can help Wikipedia by expanding it. |