Cosmochlor
| Cosmochlor | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | NaCr [Si 2 O 6 ] |
|
Mineral class (and possibly department) |
Silicates and germanates - chain silicates |
|
System no. to Strunz and to Dana |
9.DA.25 ( 8th edition : VIII / F.01) 65.01.03c.04 |
| Similar minerals | Jadeite |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 9.55 Å ; b = 8.71 Å; c = 5.27 Å β = 107.4 ° |
| Formula units | Z = 4 |
| Twinning | simple and lamellar according to {100} and {001} |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | 3.51 to 3.60; calculated: 3.60 |
| Cleavage | good after {110}, segregation after {001} |
| Break ; Tenacity | not defined |
| colour | emerald green; green or yellow in thin layers |
| Line color | light green |
| transparency | translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.740 to 1.766 n β = 1.756 to 1.778 n γ = 1.745 to 1.781 |
| Birefringence | δ = 0.015 |
| Optical character | biaxial negative |
| Axis angle | 2V = 6 to 70 ° |
| Pleochroism | strong: X = yellowish green Y = blue green, grass green Z = emerald green |
Cosmochlor is a rarely occurring mineral from the mineral class of " silicates and germanates " with the chemical composition NaCr [Si 2 O 6 ] and is therefore chemically a sodium - chromium- silicate. Structurally it belongs to the chain and band silicates and there to the group of clinopyroxenes .
Cosmochlor crystallizes in the monoclinic crystal system and develops translucent, short prismatic crystals up to about two millimeters in length with a glass-like sheen on the surfaces, which are mainly arranged in fibrous, polycrystalline mineral aggregates . In compact form, its color is described as " emerald green ", but it can appear green or yellow in thin layers.
Etymology and history
Cosmochlor was first discovered in the iron meteorite Toluca , which was found in the Municipio Jiquipilco in Mexico. The mineral was first described in 1897 by Hugo Laspeyres , who named it after its “cosmic” origin and its green color ( ancient Greek χλωρός chlōrós “light green, green yellow”).
A found in the same meteorite mineral was 1965 Clifford Frondel described and Cornelis Klein and in honor of Harold Urey as Ureyit referred. However, A. Neuhaus found in 1967 that Ureyite and Kosmochlor were the same mineral.
classification
Already in the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the cosmochlor belonged to the department of "chain and band silicates (inosilicates)", where together with aegirine , augite , diopside , essenite , jadeite , jervisite , johannsenite , Hedenbergite , Kanoite , Klinoenstatite , Klinoferrosilit , Namansilit , Natalyit , Omphacit , Petedunnit , Pigeonit , Spodumene the subgroup of "Klinopyroxene" with the system no. VIII / F.01 within the pyroxene group .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies the cosmochlor in the category of “chain and band silicates (inosilicates)”. However, this is further subdivided according to the structure of the chain formation, so that the mineral can be classified in the sub-section “Chain and ribbon silicates with 2-periodic single chains Si 2 O 6 ; Pyroxene family "can be found, where together with aegirine, jadeite, jervisite, namansilite and natalyite, the" Na-clinopyroxene, jadeite group "with the system no. 9.DA.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also classifies the cosmochlor in the "chain silicate minerals" department. Here he is a member of the " C 2 / c Klinopyroxene (Na-Klinopyroxene) " with the system no. 65.01.03c within the sub-section “Chain Silicates: Simple unbranched chains, W = 1 with chains P = 2”.
Crystal structure
Cosmochlor crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a = 9.55 Å ; b = 8.71 Å; c = 5.27 Å and β = 107.4 ° as well as 4 formula units per unit cell .
Education and Locations
In addition to jadeite, cosmochlor is an essential component in some jadeitites , but also occurs as an accessory component in some iron meteorites . Chromite- containing albite , cliftonite (pseudocubic graphite ), chlorite , chromite , daubréelite , diopside , crinovite , Richterite , roedderite and troilite can occur as accompanying minerals .
As a rare mineral formation, cosmochlor could only be detected at a few sites, whereby so far (as of 2013) around 10 sites are known. In addition to its type locality, the Toluca meteorite, the mineral also occurred in the Coahuila meteorite, which was also discovered in Mexico .
Other previously known sites are Tawmaw (Tawhmaw, Taw Maw) in the Kachin state in Myanmar, Mocchie in the Italian municipality of Condove (Piedmont), the Hime river near Itoigawa and the Ohsa mountain near Niimi on the Japanese island of Honshū, which is near in Poland Poznań discovered the Morakso meteorite , the Tersky Coast on the White Sea on the Kola Peninsula and in the Perewal open pit marble mine near the city of Slyudyanka in Irkutsk Oblast in Russia, the " Hex River Mountains " meteorite discovered in the Western Cape in South Africa and the one in the vicinity of the Barringer -Kraters in Arizona (USA) discovered "Canyon Diablo" meteorite .
literature
- H. Laspeyres : The stony mixture parts in meteor iron from Toluca in Mexico. Cosmochlor, a new cosmic mineral. In: Journal for Crystallography and Mineralogy. Volume 27, 1897, pp. 586-600. ( PDF 656 kB )
Web links
Individual evidence
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 722 (first edition: 1891).
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 621 .
- ↑ Webmineral - Kosmochlor
- ↑ a b c d e f g h i Kosmochlor. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 75.9 kB )
- ↑ Mindat - Cosmochlor
- ^ C. Frondel, C. Klein: Ureyite, NaCrSi2O6: A new meteoritic pyroxene. In: Science. Volume 149, 1965, pp. 742-744 (M. Fleischer: New mineral names. In: American Mineralogist. Volume 50, p. 2096. PDF 1.2 MB)
- ^ A. Neuhaus: About Kosmochlor (Ureyit). In: Natural Sciences. Volume 54, 1967, pp. 440–441 (M. Fleischer: New mineral names. In: American Mineralogist. Volume 53, p. 511. PDF 345.8 kB)
- ↑ Mindat - Number of locations for Kosmochlor
- ↑ Mineral finds (including Kosmochlor, Russian Космохлор) near Sljudjanka (Russian Слюдянка) ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Find location list for cosmochlor in the Mineralienatlas and in Mindat
