Difference between revisions of "Clinohumite"
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− | + | [[Image:Clinohumiteyv8.jpg|thumb|left|240px|A 9.45 ct brownish orange clinohumite tested at the Gem Testing Laboratory, Jaipur.]] | |
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+ | Clinohumite is a member of the humite group. As a gemstone it is rare, but some cut stones are reported. The given below details are (largely) abstracted from Journal of Gemmology, 2007, 30, 5/6, 303-306 "A remarkably large clinohumite". | ||
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==Crystallography== | ==Crystallography== | ||
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===Color=== | ===Color=== | ||
− | Bright yellow-orange colour resembling some hessonite and spessartine garnets. | + | Bright yellow-orange colour resembling some hessonite and spessartine garnets.<br /> |
− | Cause of | + | Cause of color: Mn |
===Diaphaneity=== | ===Diaphaneity=== | ||
Transparent | Transparent | ||
− | + | ===Refractometer=== | |
+ | |||
+ | Clinohumite has a biaxial optic character with a positive optic sign.<br /> | ||
+ | The refractive index range of clinohumite: n<sub>α</sub> = 1.628 - 1.638, n<sub>β</sub> = 1.641 - 1.654, n<sub>γ</sub> = 1.662 - 1.674.<br /> | ||
+ | The maximum birefringence ranges from 0.024 to 0.041. | ||
+ | |||
+ | For a specific stone tested (9.45 ct. brownish orange clinohumite tested at the Gem Testing Laboratory, Jaipur): R.I.: 1.646-1.670, birefringence: 0.024. | ||
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===Pleochroism=== | ===Pleochroism=== | ||
Strong trichroism: yellow, orange and brownish yellow. | Strong trichroism: yellow, orange and brownish yellow. | ||
===Specific gravity=== | ===Specific gravity=== | ||
− | S.G.: 3.21 | + | S.G.: ~ 3.21 |
===Spectrum=== | ===Spectrum=== | ||
− | + | ||
+ | [[Image:Clinohumite diffraction spectrum.jpg|thumb|left|240px|Diffraction spectrum]]<br />Brownish-orange clinohumite.<br />General cut-off till 430nm (from 400nm). | ||
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===Luminescence=== | ===Luminescence=== | ||
− | SWUV: strong orange yellow; LWUV: generally inert | + | SWUV: strong orange yellow;<br /> |
+ | LWUV: generally inert | ||
===Magnification=== | ===Magnification=== | ||
− | Inclusions: Strong | + | Inclusions: Strong color 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. |
+ | |||
+ | ==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. | ||
+ | |||
+ | ==References== | ||
+ | * G.Choudhary and Chaman Golecha, A remarkably large Clinohumite, Journal of Gemmology, 2007, 30, 5/6, pp 303-306 | ||
+ | * 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 | ||
− | === | + | * [http://www.amazon.com/gp/product/0750658568?ie=UTF8&tag=gemsandwhywelove&link_code=as3&camp=211189&creative=373489&creativeASIN=0750658568 Gems Their Sources, Descriptions and Identification'' 4th Edition (1990) - Robert Webster (6th ed.)] |
− | + | * ''Colour Encyclopedia'' - J.E. Arem ISBN 0412989115 | |
− | *Colour Encyclopedia | + | * [http://www.amazon.com/gp/product/0195149106?ie=UTF8&tag=gemsandwhywelove&link_code=as3&camp=211189&creative=373489&creativeASIN=0195149106 Introduction to Optical Mineralogy'' 3rd edition (2003), Prof. W.D. Nesse] |
− | * | ||
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Latest revision as of 17:19, 1 June 2009
Clinohumite | |
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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 |
Clinohumite is a member of the humite group. As a gemstone it is rare, but some cut stones are reported. The given below details are (largely) abstracted from Journal of Gemmology, 2007, 30, 5/6, 303-306 "A remarkably large clinohumite".
Contents
Crystallography
Monoclinic
Diagnostics
Color
Bright yellow-orange colour resembling some hessonite and spessartine garnets.
Cause of color: Mn
Diaphaneity
Transparent
Refractometer
Clinohumite has a biaxial optic character with a positive optic sign.
The refractive index range of clinohumite: nα = 1.628 - 1.638, nβ = 1.641 - 1.654, nγ = 1.662 - 1.674.
The maximum birefringence ranges from 0.024 to 0.041.
For a specific stone tested (9.45 ct. brownish orange clinohumite tested at the Gem Testing Laboratory, Jaipur): R.I.: 1.646-1.670, birefringence: 0.024.
Pleochroism
Strong trichroism: yellow, orange and brownish yellow.
Specific gravity
S.G.: ~ 3.21
Spectrum
Brownish-orange clinohumite.
General cut-off till 430nm (from 400nm).
Luminescence
SWUV: strong orange yellow;
LWUV: generally inert
Magnification
Inclusions: Strong color 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.
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.
References
- G.Choudhary and Chaman Golecha, A remarkably large Clinohumite, Journal of Gemmology, 2007, 30, 5/6, pp 303-306
- 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 Their Sources, Descriptions and Identification 4th Edition (1990) - Robert Webster (6th ed.)
- Colour Encyclopedia - J.E. Arem ISBN 0412989115
- Introduction to Optical Mineralogy 3rd edition (2003), Prof. W.D. Nesse