Shortit

from Wikipedia, the free encyclopedia
Shortit
Shortite-20224.jpg
Shortite crystals from the Poudrette quarry (Demix, Uni-Mix, Desourdy), Mont Saint-Hilaire , Canada (size 3.5 × 2.1 × 2.0 cm)
General and classification
chemical formula Na 2 Ca 2 [CO 3 ] 3
Mineral class
(and possibly department) 		Carbonates and nitrates (formerly carbonates, nitrates and borates)
System no. to Strunz
and to Dana 		5.AC.25 ( 8th edition : V / B.05)
04/14/01/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal; mm 2
Space group Amm 2 (No. 38)Template: room group / 38
Lattice parameters a  = 4.95  Å ; b  = 11.03 Å; c  = 7.11 Å
Formula units Z  = 2
Frequent crystal faces (100), ( 1 00), (011), (0 1 1), (00 1 )
Physical Properties
Mohs hardness 3 to 4.5
Density (g / cm 3 ) measured: 2.629; calculated: 2.620
Cleavage clearly after {010}
Break ; Tenacity shell-like
colour colorless, white, light yellow to dark yellow
Line color Please complete!
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.531
n β  = 1.555
n γ  = 1.570
Birefringence δ = 0.039
Optical character biaxial negative
Other properties
Chemical behavior water soluble
Special features light amber fluorescence under short-wave UV light

Shortite is a rarely occurring mineral from the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates ). It crystallizes in the orthorhombic crystal system with the composition Na 2 Ca 2 [CO 3 ] 3 , so it is chemically a sodium - calcium carbonate.

Shortit develops tabular to short-prismatic crystals several millimeters thick with a typically hemimorphic , wedge-shaped or blade -like habit with a glass-like sheen . In its pure form, Shortit is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline design, it can also appear white and, due to foreign admixtures, take on a light yellow to dark yellow color, the transparency decreasing accordingly.

Etymology and history

Shortit was first discovered in the Green River Formation in Sweetwater County of the US state Wyoming. The type material was from the slate extracted cores called "John Hay Jr. Well No. 1 ”taken from a depth of between 1258 and 1805 feet (approximately 383 to 550 meters). The mineral was described in 1939 by Joseph J. Fahey, who named it 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In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , Shortit belonged to the common mineral class of "carbonates, nitrates and borates" and there to the division of "anhydrous carbonates [CO 3 ] 2− without foreign anions ", where it belongs together with Eitelit , Fairchildit , Gregoryit , Juangodoyit , Nyerereit , Bütschliit and Zemkorit formed the unnamed group V / B.05 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the shortit to the class of "carbonates and nitrates" (the borates form a separate class here) and also to the department of “Carbonates without additional anions; without H 2 O “. However, this is further subdivided according to the element group of the cations , so that the mineral can be found according to its composition in the sub-section “ Alkali and alkaline earth carbonates”, where it is the only member of the unnamed group 5.AC.25 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the shortit, like the old Strunz system, to the class of "carbonates, nitrates and borates" and there to the department of "anhydrous carbonates". Here he is to be found as the only member of the unnamed group 04/14/01 within the subdivision of " Anhydrous carbonates with a compound formula A 2+ B 2+ 2 (CO 3 ) 4 ".

Crystal structure

Shortite crystallizes orthorhombically in the space group Amm 2 (space group no. 38) with the lattice parameters a  = 4.95  Å ; b  = 11.03 Å and c  = 7.11 Å and 2 formula units per unit cell . Template: room group / 38

properties

Under short-wave UV light , some shortites show a light amber fluorescence .

Education and Locations

Colorless shortit in sandstone from the Green River Formation , Wyoming, USA ( total size of the step : 7 × 6 × 4 cm)

Shortite forms in salt-bearing layers of dolomitic marl (Green River Formation, USA), but also occurs in kimberlite - Dykes (Canada), carbonatites and alkaline massifs (Kola, Russia). As Begleitminerale occur among other albite , apatite , Barentsit , calcite , magnetite , nahcolite , Natrit , natrolite , olivine , perovskite , phlogopite , pyrite , Trona and Villiaumit on.

As a rare mineral formation, Shortite could so far (as of 2012) only be detected at a few sites, around 30 sites being known. In addition to its type locality Green River Formation in Wyoming, the mineral occurred in the United States in the bordering states of Colorado and Utah, where it was found in several drill cores at various locations in the Piceance Basin and the Green River therein Formation and Indian Canyon .

Other locations are the “Upper Canada Gold Mine” near Gauthier ( Ontario ) and the “Poudrette” quarry on Mont Saint-Hilaire (Québec) in Canada, the “Anpeng Mine” in the Tongbai district in the Chinese province of Henan, the “Venkatampalle kimberlite” “In the Indian district of Anantapur , Daldyn in Eastern Siberia , several sites on the Russian Kola Peninsula , the Dara-i-Pioz (Darai-Pioz) glacier in the Alai Mountains in Tajikistan and Sukulu in Uganda .

See also

literature

  • Joseph J. Fahey: Shortite, a new carbonate of sodium and calcium . In: American Mineralogist . tape 24 , 1939, pp. 514-518 ( rruff.info [PDF; 258 kB ; accessed on July 27, 2017]).
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 542 .

Web links

Commons : Shortite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  291 .
  2. ↑ Webmineral - Shortite
  3. ↑ a b c d Shortite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 65  kB ]).
  4. ↑ a b c d Mindat - Shortite
  5. ↑ Mindat - Shortite