Coffinite
Mineral Coffinite is an island from the Zirkongruppe silicate having the chemical composition U4 [ (SiO4 ) (OH) 4]. It crystallizes in the tetragonal crystal system and rarely develops small crystals of more than 20 microns. He usually can be found in the form of colloidal and nieriger crusts or radialstrahliger, fibrous, bulky or pulviger mineral aggregates from black to brown in color. Coffinite is abundant in various localities, but overall not very common.
Special Features
The mineral is classified as very highly radioactive due to its uranium content of up to 72.6 % and has a specific activity of 130.016 kBq / g (compared to natural potassium 31.2 Bq / g).
Etymology and history
Coffinite was first discovered in the " La Sal No.. 2 Mine " on Beaver Mesa in Mesa County in the U.S. state of Colorado and described in 1956 by LR Stieff, TW Stern and AM Sherwood, designated to his pioneering work to the study of the minerals by the American geologist Reuben Clare Coffin ( 1886-1972 ) uranium deposits of the Colorado plateau to honor.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of coffinite the mineral class of " silicates and Germanates " and then to the Department of " island silicates ( nesosilicates ) " where he along with Hafnon, Reidit, Thorite, thorogummite and zircon formed a distinct group.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Coffinite also included in the category of " silicates and Germanates " and then in the Department of the " island silicates ( nesosilicates ) ". This division, however, is now further subdivided by the presence of other anions and the coordination of the cations, so that the mineral is found according to its composition in the subdivision of " island silicates without additional anions with cations in oktahedraler and usually greater coordination," where, also the unnamed group 9.AD.30 together with Hafnon, thorite, and zircon thorogummite.
The classification of minerals according to Dana assigns the coffinite in the class of " silicates and Germanates " and then in the Department of the " island silicate minerals " one. Here he is with zircon, Hafnon, Thorite, thorogummite and Stetindit in the " Zirkongruppe " with the system no. 51.05.02 within the subdivision of the " island silicates: only with cations SiO4 groups in > coordination " to find.
Modifications and varieties
Uranothorit is a variety with high levels of thorium.
Education and Locations
Coffinite forms in hydrothermal veins and hydrothermally mineralized fault zones (eg Dolni Rozinka, Czech Republic) before. Furthermore, it is found in sedimentary uranium deposits in sandstones (eg Colorado). Accompanying minerals include uraninite, thorite, pyrite, marcasite, roscoelite and various clay minerals and amorphous organic substances.
Worldwide, Coffinite so far (as of 2011) are detected at around 500 localities. Apart from its type locality was the mineral in the United States or in many other places in the states of Arizona, Colorado, New Mexico, Texas, Utah and Wyoming and in Koyuk and Ketchikan, Alaska, at the Kern River and Sonora Pass in California, in East Granby (Hartford County) in Connecticut, in the Stanley Basin ( Custer County, Idaho ), the uranium deposit in Dawes County, Nebraska, in Humboldt County and the Reese River ( Lander County ) in Nevada, in Bedford ( Westchester County) in New York, at Lakeview ( Lake County) and the McDermitt district ( Malheur County) in Oregon, at Jim Thorpe in Pennsylvania, in fall River County, South Dakota, in Pittsylvania County, Virginia, in Stevens County and Castle Peak ( Whatcom County) in Washington.
Known localities are mainly deposits on the Colorado Plateau ( Woodrow Mine, New Mexico ), where the mineral pitchblende in addition as the main carrier of uranium acts. The same applies to the " Ogame Mine" in Japan.
In Germany Coffinite place along with pitchblende, especially in the Black Forest in Baden- Württemberg; in Franconia, in the Upper Palatinate in Bavaria and Miltach; in the Hessian Odenwald; at several sites in Rhineland -Palatinate; at Mansfeld in Saxony -Anhalt; in the Erzgebirge and Vogtland in Saxony and Thuringia in Ronneburg.
In Austria Coffinite was at Erzberg hut in Carinthia, the forest tunnel on the A9 near forest on Schoberpaß in Styria and the Graschberg at Thierenbach (municipality Wildschönau ) in Tyrol.
In Switzerland, the mineral Lavey- les- Bains found in Kaisten AG and Riniken in the canton of Aargau, in the canton of Vaud and in Collonges VS and Marécottes in the canton of Valais.
Other localities lie in Egypt, Argentina, Australia, Bolivia, Brazil, Bulgaria, Canada, China, Czech Republic, Finland, France, Gabon, Greenland, Guyana, India, Kazakhstan, Mongolia, New Zealand, Niger, Nigeria, Norway, Poland, Portugal, Russia, Zambia, Sweden, Slovakia, Slovenia, Spain, South Africa, Hungary, Uzbekistan, the United Kingdom ( UK) and in the United States of America (USA).
Crystal structure
Coffinite crystallized tetragonal in the space group I41/amd ( Raumgruppen-Nr. 141) with the lattice parameters a = 6.99 Å and c = 6.26 Å and four formula units per unit cell.
Coffinite belongs structurally to the zirconium Titanitgruppe. By substituting significant amounts of other elements may occur, particularly thorium instead of uranium. There is a broad miscibility between coffinite and thorite. Because of its own radioactivity, the crystal lattice is often destroyed and the metamict mineral.
Coffinite one of the island silicates, that is, the SiO4 tetrahedra are not interconnected.
Use
Coffinite is an economically important mineral for the extraction of uranium.
Security measures
Due to the high radioactivity of the mineral samples should be stored in a dust - and radiation- proof containers, especially but never in living, sleeping and working areas. Similarly, inclusion in the body ( incorporation) should be definitely prevented and the safety of direct body contact and worn when handling the mineral mask and gloves