Huntite

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Huntite
Huntita de Montcada.jpg
General and classification
chemical formula CaMg 3 [CO 3 ] 4
Mineral class
(and possibly department) 		Carbonates and nitrates
System no. to Strunz
and to Dana 		5.AB.25 ( 8th edition : V / B.03)
04/14/03/01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol trigonal trapezoidal; 32
Space group R 32 (No. 155)Template: room group / 155
Lattice parameters a  = 9.50  Å ; c  = 7.82 Å
Formula units Z  = 3
Physical Properties
Mohs hardness <3
Density (g / cm 3 ) measured: 2.696; calculated: 2.875
Cleavage slightly mussel-like
Break ; Tenacity brittle
colour colorless to white
Line color White
transparency translucent
shine frosted
Crystal optics
Refractive indices n ω  = 1.622
n ε  = 1.615
Optical character uniaxial negative

Huntite is a rarely occurring minerals from the mineral class of "carbonates and nitrates" with the chemical composition CaMg 3 [CO 3 ] 4 and is thus chemically seen a Calcium - magnesium - carbonate .

Huntite crystallizes in the trigonal crystal system , but develops only microscopic, tabular and rhombohedral crystals up to about 1 μm in size. It is mostly found in the form of fibrous to compact or earthy to powdery, lime-like masses. The mineral is translucent and, in its compact form, matt white.

Etymology and history

Huntite was discovered in 1943 by George T. Faust during his studies of the distribution of dolomite in magnesite samples from the magnesite deposit "Ala-Mar" (also Currant Creek or Manzoni ) in White Pine County of the US state Nevada . The material analyzed appeared to be magnesite in physical properties, but the flame test also indicated the presence of calcium . Through further analyzes, Faust finally succeeded in proving that it was a new mineral and published his results in 1953 in the mineralogical magazine "American Mineralogist". He named the mineral in honor of his former teacher, the former professor of mineralogy at the University of Michigan Walter Frederick Hunt (1882-1975).

Type material of the mineral is available from Harvard University in Cambridge, Massachusetts under catalog no. 106372 and in the National Museum of Natural History in Washington, DC under catalog no. 112519 kept.

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the huntite belonged only to the common mineral class of "carbonates,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 together with ankerite , benstonite , dolomite, ewaldite , kutnohorite , minrecordite and norsethite the "dolomite group" with the system no. V / B.03 formed.

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 huntite to the newly defined class of “carbonates and nitrates” (the borates now form a class of their own), but there, too the division of “carbonates without additional anions; without H 2 O “. This is further subdivided according to the affiliation of the cations involved to the respective chemical group, so that the mineral can be found according to its composition in the subsection " alkaline earth (and other M 2+ ) carbonates", where it is the only member of the unnamed group 5. AB.25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns huntite to the class of "carbonates, nitrates, borates" and there in the department of "anhydrous carbonates". Here he is the only member of the unnamed group 04/14/03 within the sub-section “Anhydrous carbonates with a compound formula A 2+ B 2+ 2 (CO 3 ) 4 ”.


Crystal structure

Huntite crystallizes trigonally in the space group R 32 (space group no. 155) with the lattice parameters a  = 9.50  Å and c  = 7.82 Å as well as 3 formula units per unit cell . Template: room group / 155

Education and Locations

Huntite is usually formed by precipitation in various sediments , including the evaporation of seawater in lagoon sediments or salt lakes, but also from cold water such as at its type locality , the magnesite deposit "Ala-Mar" in Nevada, USA. Under these formation conditions, the accompanying minerals are mainly gypsum and halite , occasionally celestine and magnesite and, to a lesser extent , dolomite, calcite , aragonite and polyhalite .

Huntite can also arise from limnic sediments as the erosion product of ultrabasic rocks , where it occurs, among other things, in paragenesis with hydromagnesite and magnesite.

Furthermore, huntite can form secondary to the weathering of magnesium-rich rocks.

As a rare mineral formation, Huntite could only be detected in a few places, whereby so far (as of 2016) around 65 sites are known. In addition to its type locality "Ala-Mar" and the nearby prospecting "Snowball" in White Pine County, the mineral was also found in Nevada near Austin in Lander County and in the Sierra Magnesite mine near Gabbs in Nye County . Other well-known sites in the USA are in the Cimarron Mountains near Cimarron ( Pima County ) in Arizona; in the quarries at Crestmore in Riverside County , in the Clear Creek Claim near New Idria in San Benito County and in the "Pacific Limestone" quarry near Santa Cruz in the county of California of the same name; in the "Hunting Hill" quarry near Rockville , Maryland; in the Carlsbad Caverns in Eddy County and in the Fossil Forrest (San Juan Basin, San Juan County ) in New Mexico; at the Green Mountain Mine at Day Book in Yancey County , North Carolina; at Cedar Hill in Lancaster County , Pennsylvania; in the Wind Cave in Custer County , South Dakota; and in Little Rocky Prospection in Beaver County , Utah.

In Germany, huntite has so far only been discovered in the Haidberg quarry near Zell and in the Marthahütte quarry near Marktredwitz in Bavaria and in the Lichtenberg opencast mine in Thuringia.

In Austria, the mineral was found in a graphite deposit near Raintal (Dürnberg) in the market town of Schönbühel-Aggsbach and in several quarries near Amstall and Eibenstein in Lower Austria and in a basalt quarry near Klöch in Styria.

Other locations are in Australia, Chile, France, Greece, Italy, Japan, Canada, Pakistan, Russia, Slovakia, Spain, South Africa, the Czech Republic, Turkey, Hungary and Uzbekistan.

See also

literature

  • George T. Faust: Huntite, Mg 3 Ca (CO 3 ) 4 , a new mineral . In: American Mineralogist . tape 38 , 1953, pp. 4–24 ( rruff.info [PDF; 1.3 MB ]).
  • WA Dollase, RJ Reeder: Crystal structure refinement of huntite, CaMg 3 (CO 3 ) 4 , with X-ray powder data . In: American Mineralogist . tape 71 , 1986, pp. 163–166 ( rruff.info [PDF; 404 kB ]).
  • W. Wetzenstein: Limnic huntite-hydromagnesite-magnesite deposits in Macedonia / Northern Greece . Springer, 1975, doi : 10.1007 / BF00206528 .

Web links

Commons : Huntite  - 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.  288 .
  2. ↑ Webmineral - Huntite
  3. ↑ a b c d e f g Huntite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
  4. ↑ George T. Faust: Huntite, Mg 3 Ca (CO 3 ) 4 , a new mineral . In: American Mineralogist . tape 38 , 1953, pp. 4–24 ( rruff.info [PDF; 1.3 MB ]).
  5. ↑ a b c Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  532 .
  6. ↑ Mindat - Number of localities for Huntite
  7. ↑ a b List of locations for huntite in the Mineralienatlas and Mindat