Emmonsite
| Emmonsite | |
|---|---|
 |
|
| General and classification | |
| other names |
Durdenite |
| chemical formula | Fe 3+ 2 (Te 4+ O 3 ) 3 · 2H 2 O |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.JM.10 ( 8th edition : IV / K.09) 03/34/03/01 |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Room group (no.) | P 1 (No. 2) |
| Lattice parameters |
a = 7.90 Å ; b = 8.00 Å; c = 7.62 Å, α = 96.7 °; β = 95.0 °; γ = 84.5 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 4.52 to 4.55; calculated: 4.719 |
| Cleavage | perfect according to {010}, good according to {100} and {001} |
| colour | light green to yellow green |
| Line color | Please complete |
| transparency | translucent to opaque |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.962 n β = 2.090 n γ = 2.100 to 2.120 |
| Birefringence | δ = 0.138 to 0.158 |
| Optical character | biaxial negative |
| Axis angle | 2V = 23 ° (measured); 28 to 48 ° (calculated) |
Emmonsite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the triclinic crystal system having the composition Fe 3+ 2 (Te 4+ O 3 ) 3 · 2H 2 O, is so chemically seen a iron - tellurite .
Emmonsite usually develops stem-like to needle-like or thin tabular crystals , but is also found in the form of fibrous, tufted to spherical or massive mineral aggregates and crusty coatings of light green to yellow-green color. The mineral is generally translucent to opaque, but thin layers or small grains can also be transparent. The surfaces of the crystals have a glass-like sheen .
Etymology and history
Emmonsite was first discovered near Tombstone in Cochise County (Arizona) in the United States and described in 1885 by William Francis Hillebrand , who named the mineral after the US geologist Samuel Franklin Emmons .
1890 Dana and Wells described a new mineral from the mine "El Plomo" in the district Ojojona in Honduras and called it Durdenit by Henry S. Durden , who had asked the mineral sample. Comparative analyzes with emmonsite samples from Tombstone and Cripple Creek (Colorado), however, confirmed the identity of durdenite and emmonsite. The name durdenite was therefore discredited and is now considered a synonym for the emmonsite.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the emmonsite belonged to the division of " sulfites , selenites and tellurites ", where it formed the unnamed group IV / K.09 together with blakeit , poughit , rodalquilarite and sonoraite .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies emmonsite in the expanded division of " antimonites , bismuthites , sulphites, selenites and tellurites". This is further subdivided according to the possible presence of additional anions and / or water of crystallization (H 2 O), so that the mineral is classified according to its composition in the sub-section “Tellurite without additional anions; with H 2 O ”, where only together with Blakeit the“ Emmonsit group ”with the system no. 4.JM.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns emmonsite to the class of "sulfates, chromates and molybdates", but also to the category of "selenites, tellurites and sulfites" there. Here he is to be found as the only member of the unnamed group 34.03.03 within the subdivision " 34.03 Selenites - Tellurites - Sulphites ".
Education and Locations
Emmonsite is formed as a secondary mineral during the weathering ( oxidation ) of tellurite or native tellurium . Besides these appear as more assemblages under a different Cuzticit , Eztlit , gold , Mackayit , pyrite , Rodalquilarit and Sonorait on.
As a rare mineral formation, Emmonsite has only been found at a few sites so far, with around 40 sites being known (as of 2013). In addition to its Tombstone type locality , the mineral could be found in other locations in the Tombstone Hills in Arizona, in Calaveras County in California, near Cripple Creek in Colorado, in several locations in Esmeralda County in Nevada, in the "Lone Pine Mine" in Catron County , near Silver City and in Hidalgo County in New Mexico, in the "Clinton Mine" in Lawrence County in South Dakota and in the "Gold Chain Mine" in Juab County in Utah.
Other locations include Chile, China, Honduras, Japan and Mexico.
Crystal structure
Emmonsite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 7.90 Å ; b = 8.00 Å; c = 7.62 Å; α = 96.7 °; β = 95.0 ° and γ = 84.5 ° as well as 2 formula units per unit cell .
See also
literature
- WF Hillebrand : Emmonsite, a ferric tellurite , In: Proceedings of the Colorado Scientific Society , Volume 2 (1885), pp. 20–23 ( PDF 136.9 kB )
- Clifford Frondel, Frederick H. Pough: Two new tellurites of iron: Mackayite and Blakeite. with new data on emmonsite and "durdenite" , In: American Mineralogist , Volume 29 (1944), pp. 211–225 ( PDF 943.5 kB )
Web links
Individual evidence
- ↑ 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. 279 .
- ↑ Webmineral - Emmonsite
- ↑ a b c Emmonsite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 68.1 kB )
- ↑ a b c d Mindat - Emmonsite
- ^ Clifford Frondel, Frederick H. Pough: Two new tellurites of iron: Mackayite and Blakeite. with new data on emmonsite and "durdenite" , In: American Mineralogist , Volume 29 (1944), pp. 211–225 ( PDF 943.5 kB )
- ↑ Mindat - Number of localities for Emmonsit