Kernite

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Kernite
Kernitas.jpg
General and classification
chemical formula Na 2 [B 4 O 6 (OH) 2 ] • 3H 2 O
Mineral class
(and possibly department)
Borates (formerly: "Carbonates, Nitrates and Borates")
System no. to Strunz
and to Dana
6.DB.05 ( 8th edition : V / J.04)
04/26/05/01
Similar minerals Borax , Probertite , Tincalconite , Ulexite
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / a (No. 14, position 3)Template: room group / 14.3
Lattice parameters a  = 15.68  Å ; b  = 9.16 Å; c  = 7.02 Å
β  = 108.9 °
Formula units Z  = 4
Twinning after {011}
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 1.906 (3); calculated: 1.905
Cleavage perfect according to {100} and {001}, good according to { 2 01}
Break ; Tenacity splintery, occasionally fibrous
colour colorless, white
Line color White
transparency transparent to opaque
shine Glass gloss, silk gloss, matt
Crystal optics
Refractive indices n α  = 1.454
n β  = 1.472
n γ  = 1.488
Birefringence δ = 0.034
Optical character biaxial negative
Axis angle 2V = measured: 80 °; calculated: 84 °
Pleochroism unavailable
Other properties
Special features soluble in water

Kernite (also rasorite ) is a rarely occurring mineral from the mineral class of " borates " (formerly: "carbonates, nitrates and borates", see classification ) with the chemical composition Na 2 [B 4 O 6 (OH) 2 ] · 3H 2 O and is therefore chemically a water-containing sodium tetraborate .

Kernite crystallizes in the monoclinic crystal system and develops mostly colorless to white, isometrically shaped crystals with a glass-like sheen on the surfaces. Often, however, silk-gloss, fibrous, granular or massive aggregates of up to 3.5 m in size are also found.

Etymology and history

Kernite was first found in the Kramer Borate deposit "Rich Station" near Boron in Kern County in California and described in 1927 by Waldemar Theodore Schaller , who named the mineral after its type locality (Kern County).

Type material of the mineral is stored at Harvard University near Cambridge, Massachusetts (Register No. 88508) and the National Museum of Natural History of Washington, DC, USA (Register No. 95643).

classification

In the now outdated, but still common 8th edition of the mineral classification according to Strunz , the kernite belonged to the common mineral class of " carbonates , nitrates and borates" and there to the department of "chain borates", where it formed an independent group without any further relatives.

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and is used by the International Mineralogical Association (IMA), assigns kernite to the now independent class of "borates" and there in the department of "tetraborates". This department is, however, further subdivided according to the crystal structure, so that the mineral can be found according to its structure in the subdivision "Chain and ribbon tetraborates (Ino-Tetraborates)", where it is the only member of the unnamed group 6.DB.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the kernite, like the outdated 8th edition of Strunz's system, to the common class of "carbonates, nitrates and borates", but there in the department of "hydrous borates with hydroxyl or halogen ”. Here he is the only member of the unnamed group 04/26/05 within the subdivision of “ Hydrogen borates with hydroxyl or halogen ”.

Crystal structure

Kernite crystallizes monoclinically in the space group P 2 1 / a (space group no. 14, position 3) with the lattice parameters a  = 15.68  Å ; b  = 9.16 Å; c  = 7.02 Å and β = 108.9 ° and 4 formula units per unit cell . Template: room group / 14.3

The crystal structure of kernite consists of corner-sharing BO 4 - tetrahedra , which form parallel to the b-axis chains and are mutually connected with B (OH) groups.

properties

Kernit is water-soluble, so it must be kept as a mineral sample protected from moisture.

Education and Locations

Several large crystals from the US Borax Mine near Boron, California

Kernite forms weak contact metamorphosis from borax and sedimentation in boron-containing deposits . Accompanying minerals include borax, inyoite , ulexite and colemanite .

So far (as of 2011), Kernit has been detected at 10 sites worldwide. One of the most important deposits of the mineral is the Mojave Desert in California in the east of Kern County .

Kernite was also found near Otis in San Bernardino County , also in California , in the Salta province in Argentina, Catalonia in Spain and in the borate deposit near Kırka in the Turkish province of Eskişehir.

use

Despite its rarity, kernite with a boron content of up to 14.9% is an important ore for the extraction of this element for the chemical industry .

See also

literature

  • Waldemar T. Schaller: Kernite, a new sodium borate . In: American Mineralogist . tape 12 , 1927, pp. 24–25 ( rruff.info [PDF; 141 kB ; accessed on October 24, 2017]).
  • Kernite . 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; 66 kB ; accessed on October 24, 2017]).
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Dörfler Verlag GmbH, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 134 .

Web links

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

Individual evidence

  1. a b c d e f 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.  348 .
  2. a b Webmineral - Kernite (English)
  3. a b c d e f Kernite . 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; 66  kB ; accessed on October 24, 2017]).
  4. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  590–591 (first edition: 1891).
  5. a b c d e f g Mindat - Kernite (English)
  6. ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  562 .