Shortite
Shortite is a rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly known as carbonates, nitrates and borates ). It crystallizes in the orthorhombic crystal system with the composition Na2Ca2 [ CO3 ] 3, is so chemically seen a sodium -calcium carbonate.
Shortite developed tabular to short prismatic crystals of several millimeters thickness, typically hemimorphem, wedge-shaped or schneidenartigem habit with glass-like shine. In its pure form Shortite is colorless and transparent. But it may also appear white and accept by foreign admixtures a light yellow to dark yellow color by multiple refraction due to lattice defects or polycrystalline training, the transparency decreases accordingly.
Special Features
Under short-wave UV light indicate some Shortite a light amber -colored fluorescence.
Etymology and history
Was first discovered Shortite in the Green River Formation in Sweetwater County of the U.S. state of Wyoming. The type material was taken from the slate the cores with the name " John Hay Jr. Well No. 1 " removed, which originate from a depth of 1258-1805 feet ( equivalent to about 383-550 meters). This has been described mineral 1939 by Joseph J. Fahey, of which it is named after Professor Dr. Maxwell N. Short of the University of Arizona.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz Shortite belonged to common mineral class of " carbonates, nitrates and borates " and then to the Department of " water clear carbonate [ CO3 ] 2 - without foreign anions ", where he, together with Eitelit, Fairchildit, Gregoryit, Juangodoyit, Nyerereit, Bütschliit and Zemkorit the unnamed group V/B.05 formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Shortite in the class of " carbonates and nitrates " ( here, the borates form a separate class) and there is also in the Department of " carbonates without additional anions, without H2O" one. However, this is further subdivided according to the element group membership of the cations, so that the mineral is found according to its composition in the subsection " alkali and alkaline earth metal carbonates ", where it forms the unnamed group 5.AC.25 the only member.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Shortite as the old Strunz classification in the category of " carbonates, nitrates and borates " and there in the department of " water clear carbonates " one. Here he is the only member of the unnamed group 14:04:01 within the sub-division of " water clear with carbonates composite formula A2 B2 2 (CO3 ) 4" to find.
Education and Locations
Shortite forms in salt- bearing strata of dolomitic marl ( Green River Formation, USA), but also occurs in kimberlite dykes (Canada), carbonatites and alkaline massifs ( Kola, Russia). Accompanying minerals occur among others albite, apatite, Barentsit, calcite, magnetite, Nahcolith, Natrit, Natrolite, olivine, perovskite, phlogopite, pyrite, Trona and Villiaumit.
A rare mineral formation Shortite has so far (as of 2012) detected only at a few localities, of which approximately 30 localities are known. Apart from its type locality Green River Formation in Wyoming, the mineral in the United States occurred nor in the neighboring states of Colorado and Utah, where it was found in several cores taken at different locations of the Piceance Basin or lying in Green River formation and the Indian Canyon were taken.
Other localities are the " Upper Canada Gold Mine" near Gauthier (Ontario ) and the quarry " Poudrette " at Mont Saint- Hilaire (Québec) in Canada, the " Anpeng Mine " in the circle Tongbai in the Chinese province of Henan, the " Venkatampalle kimberlite " in the Indian district of Anantapur, Daldyn in Eastern Siberia, several points Fund on the Russian Kola Peninsula, the glacier Dara -i - Pioz ( Darai - Pioz ) in the Alai Mountains in Tajikistan and Sukulu in Uganda.
Crystal structure
Shortite crystallizes in the orthorhombic space group Amm2 ( Raumgruppen-Nr. 38) with the lattice parameters a = 4.95 Å; b = 11.03 Å and c = 7.11 Å and two formula units per unit cell.