Clinohumite
Clinohumite | |
---|---|
Chemical composition | Magnesium silicate |
Hardness | 6 |
Optic nature | Biaxial + |
Refractive index | 1.628 - 1.674 |
Birefringence | 0.024 - 0.041 |
Specific gravity | ~ 3.21 |
Lustre | Vitreous |
Pleochroism | Strongly trichroic |
Fluorescence |
SWUV: strong orange yellow |
Contents
Occurrence
Geographical 0ccurrence: Gem quality Clinohumite is known to occur in two important localities - The Pamir mountains (at Kukh-i-lal, Sumdzin and Changin); in Tajikistan in association with spinel and in the Taymyr region (Basin of Kotui river) in Siberia; Also in Mahenge, Tanzania.
Crystallography
Monoclinic
Diagnostics
Color
Bright yellow-orange colour resembling some hessonite and spessartine garnets.
Cause of color: Mn
Diaphaneity
Transparent
Refractometer
R.I. variable 1.646-1.670 for a specific stone tested (9.45 ct. brownish orange clinohumite tested at the Gem Testing Laboratory, Jaipur).
D.R.: 0.024 Anisotropic, biaxial positive.
Pleochroism
Strong trichroism: yellow, orange and brownish yellow.
Specific gravity
S.G.: 3.21
Spectrum
Orange-brown clinohumite.
General cut-off till 430nm (from 400nm).
Luminescence
SWUV: strong orange yellow;
LWUV: generally inert
Magnification
Inclusions: Strong colour and growth zoning, flat paralles reflective planes, fluid like inclusions similar to trichites in tourmaline. Such liquid inclusions along with doubling appear very much like tourmaline; tube like inclusions; sometimes swirly zones.
References
- G.Choudhary and Chaman Golecha, A remarkably large Clinohumite, Journal of Gemmology, 2007, 30, 5/6, pp 303-306
- Colour Encyclopedia of Gemstones by J.E.Arem
- Henn, U., Hyrsl, J., and Milisenda, C.C., Gem Quality clinohumite from Tajikistan and the Taymyr region, Northern Siberia. Journal of Gemmology, 27(6), 335-9
- Hyrsl, J., 2001. Gem News International. Spinel with clinohumite from Mahenge, Tanzania, Gems and Gemology, 37(2), 144-5
- Laurs, B.M., and Quinn, E.P., 2004. Gem News International. Clinohumite from Mahenge, Tanzania. Gems and Gemology, 40(4), 337-8
- Gems by Webster.