Emmonsite
- Durdenit
Emmonsite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the triclinic crystal system with the composition Fe3 2 ( Te4 O3) 3.2 H2O, is so chemically seen an iron - tellurite.
Emmonsite developed mostly columnar to acicular crystals or dünntafelige, but is also found in the form of fibrous, tufted to spherical or massive mineral aggregates and crusty coating 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 shine.
Etymology and history
Was first discovered Emmonsite near Tombstone in Cochise County ( Arizona). Throughout the United States and described in 1885 by William Francis Hillebrand, who named the mineral after the American geologist Samuel Franklin Emmons
Dana and Wells 1890 described a new mineral from the mine " El Plomo " in the district Ojojona to Honduras and called it Durdenit by Henry S. Durden, who had asked the mineral sample. Comparative analyzes with Emmonsitproben from Tombstone and Cripple Creek ( Colorado), however, demonstrated the identity of Durdenit and Emmonsite. The name Durdenit was therefore discredited and is now considered a synonym for the Emmonsite.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Emmonsite belonged to the department of " sulphites, Selenite and Tellurite ", where he led the unnamed group formed together with Blakeit, Poughit, Rodalquilarit and Sonorait IV/K.09.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Emmonsite in the Advanced section of the " Antimonite, Bismuthite, sulfites, Selenite and Tellurite " one. This is also further divided according to the possible presence of additional anions and / or crystal water ( H2O), so that the mineral which according to its composition in the subsection " Tellurite without additional anions, with H2O" is to find where it only together with Blakeit " Emmonsite group " with the system no. 4.JM.10 forms.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Emmonsite contrast, in the class of " sulfates, chromates and molybdates ," there but also in the department of " Selenite, Tellurite and sulphites " one. Here he is the only member of the unnamed group 34.03.03 within the subdivision " 34.03 Selenite - sulfites - Tellurite " to find.
Education and Locations
Emmonsite forms as a secondary mineral in the weathering (oxidation) of tellurite or tellurium solid. Besides these occur, you still Cuzticit, Eztlit, gold, Mackayit, pyrite, and Rodalquilarit Sonorait more than parageneses.
A rare mineral formation Emmonsite could be proven so far only in a few localities, of which approximately 40 localities known as apply (as of 2013). Apart from its type locality Tombstone was the mineral nor in other places in the Tombstone Hills, Arizona, in Calaveras County, California, near Cripple Creek, Colorado, at several locations in Esmeralda County, Nevada, in the " Lone Pine Mine" in Catron County, near Silver City and the Hidalgo County, New Mexico, in the " Clinton Mine" in Lawrence County, South Dakota, as well as the "Gold Chain Mine" in Juab County, Utah be found.
Other localities lie among others in Chile, China, Honduras, Japan, and Mexico.
Crystal structure
Emmonsite crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 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 ° and two formula units per unit cell.