Leucite
| Leucite | ||
|---|---|---|
Specific gravity 2.45–2.50 | | |
| Optical properties | Uniaxial (+) | |
| Refractive index | nω = 1.508 nε = 1.509 | |
| Birefringence | δ = 0.001 | |
| References | [2][3] | |
Leucite (from the Greek word leukos meaning white) is a
monoclinic individuals, which are optically biaxial and repeatedly twinned, giving rise to twin-lamellae and to striations on the faces. When the crystals are raised to a temperature of about 500 °C they become optically isotropic and the twin-lamellae and striations disappear, although they reappear when the crystals are cooled again. This pseudo-cubic character of leucite is very similar to that of the mineral boracite
.
The crystals are white or ash-grey in colour, hence the name suggested by
specific gravity 2.47. Inclusions of other minerals, arranged in concentric zones, are frequently present in the crystals. On account of the color and form of the crystals the mineral was early known as 'white garnet'. French authors in older literature may employ René Just Haüy
's name amphigène, but 'leucite' is the only name for this mineral species that is recognised as official by the International Mineralogical Association.
References
Wikimedia Commons has media related to Leucite.
- S2CID 235729616.
- ^ Leucite on Mindat
- ^ Handbook of Mineralogy
- ISBN 978-1-4093-8659-9.
- This article incorporates text from a publication now in the public domain: Spencer, Leonard James (1911). "Leucite". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 16 (11th ed.). Cambridge University Press. pp. 503–504.
