Cosnarite

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Cosnarite
Kosnarite-Albite-180065.jpg
Cream-white Kosnarite on albite from the Jenipapo District, Jequitinhonha Valley, Minas Gerais , Brazil (size: 7.9 cm × 5.3 cm × 1.4 cm)
General and classification
other names

IMA 1991-022

chemical formula KZr 2 [PO 4 ] 3
Mineral class
(and possibly department)
Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana
8.AC.60 ( 8th edition : VII / A.17)
04/38/12/01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral; 3  2 / m
Space group R 3 c (No. 167)Template: room group / 167
Lattice parameters a  = 8.71  Å ; c  = 23.89 Å
Formula units Z  = 6
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) measured: 3.194 (2) D (calc.) = 3.206
Cleavage perfect {10 1 2}; indistinct after {0001}
Break ; Tenacity clamshell; brittle
colour light blue to blue-green, bluish-gray to almost colorless
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.656
n ε  = 1.682
Birefringence δ = 0.026
Optical character biaxial positive

Kosnarite is a very rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition KZr 2 [PO 4 ] 3 and thus, chemically speaking, a potassium - zirconium - phosphate .

Kosnarite crystallizes in the trigonal crystal system and develops rhombohedral or twinning pseudocubic crystals with a glass-like sheen on the surfaces.

In its pure form, Kosnarite is colorless and transparent. However, due to foreign admixtures , it can also take on a light blue to blue-green or bluish-gray color, with the transparency decreasing accordingly.

Etymology and history

Was first discovered Kosnarit in a pegmatite - quarry on Mount Mica in Paris in the State of Maine and described in 1993 by Michael E. Brown Field, Eugene E. Foord, Stephen J. Sutlej, Theodore Botinelly that the minerals by the mineral dealer Richard Kosnar ( 1946–2006) from Colorado.

Since material from the nearby quarry on Black Mountain near Rumford was also used for the analysis of the composition , this site is also considered a type locality for the Kosnarite.

Type material of the mineral is in the National Museum of Natural History in Washington, DC, USA under the catalog no. 170369 and 170370 kept.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the kosnarite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the division of "anhydrous phosphates [PO 4 ] 3− , without foreign anions ", where he was the only member of the unnamed group VII / A.17 .

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns cosnarite to the category of “phosphates etc. without additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the subsection “With medium-sized and large cations”, where it is the only member of the unnamed group 8.AC.60 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Kosnarit to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc.". Here he is to be found as the only member / together with in the unnamed group April 38, 2012 within the subdivision “Anhydrous phosphates etc., A + XO 4 ”.

Crystal structure

Kosnarite crystallizes trigonal in the space group R 3 c (space group no. 167) with the lattice parameters a  = 8.71  Å and c  = 23.89 Å and 6 formula units per unit cell . Template: room group / 167

Education and Locations

Pale yellow, pseudocubic cosnarite on albite from the Jenipapo district, Minas Gerais, Brazil ( total size of the sample: 3.1 cm × 2.6 cm × 1.7 cm)

Kosnarite forms in the late phase of hydrothermal transformations in granitic pegmatites , possibly from beryl and zircon .

The mineral was found in paragenesis with albite , eosphorite , fluoroapatite , moraesite , quartz , siderite and zircon at its type localities and so far the only sites in the USA, Mount Mica and Black Mountain in Maine . In addition, in the granite quarry were Wycheproof in the Australian Shire of Buloke (Victoria) as a further Begleitminerale still Cyrilovit , Schörl , Selwynit and Wycheproofit found.

The only other known sites are the Jorge Pegmatite in the Jenipapo district on the Rio Jequitinhonha (Jequitinhonha Valley) in the Brazilian state of Minas Gerais and the Chaquicocha open pit mine in the Peruvian department of Cajamarca, which is part of the Yanacocha gold mine .

See also

literature

  • Michael E. Brownfield, Eugene E. Foord, Stephen J. Sutley, Theodore Botinelly: Kosnarite, KZr2 (PO4) 3, a new mineral from Mount Mica and Black Mountain, Oxford County, Maine . In: American Mineralogist . tape 78 , 1993, p. 653–656 ( rruff.info [PDF; 431 kB ]).

Web links

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

Individual evidence

  1. a b c d 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.  434 .
  2. a b Kosnarite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
  3. a b c Mindat - Kosnarite
  4. Find location list for Kosnarite in the Mineralienatlas and in Mindat