Clinoclase

from Wikipedia, the free encyclopedia
Clinoclase
Clinoclase-Cornwallite-Strashimirite-289142.jpg
Deep blue shiny crystal aggregates from Klinoklas on a blue-green matrix of Cornwallite and Strashimirite ( overall size : 4.5 × 2.9 × 1.1 cm)
General and classification
other names
  • Abichit
  • Aphanesite
  • Siderochalcite
  • Emitter ore
chemical formula Cu 3 [(OH) 3 | AsO 4 ]
Mineral class
(and possibly department) 		Phosphates and arsenates
System no. to Strunz
and to Dana 		8.BE.20 ( 8th edition : VII / B.13)
03/31/01/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) P 2 1 / c (No. 14)
Lattice parameters a  = 7.26  Å ; b  = 6.46 Å; c  = 12.38 Å
β  = 99.5 °
Formula units Z  = 4
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) 4.38 to 4.42
Cleavage completely after {001}
Break ; Tenacity uneven; brittle
colour dark green blue to almost black
Line color bluish green
transparency transparent to translucent
shine Glass gloss to pearlescent
Crystal optics
Refractive indices n α  = 1.730
n β  = 1.870
n γ  = 1.910
Birefringence δ = 0.180
Optical character biaxial negative
Axis angle 2V = measured: 30 °; calculated: 52 °

Klinoclase , also known in mining as emitter or under the synonymous names abichite , aphanesite and siderochalcite , is a rather seldom occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the composition Cu 3 [(OH) 3 | AsO 4 ], so it is chemically a basic copper arsenate.

Clinoclase is transparent to translucent and develops only small, tabular or fine-needle to prismatic crystals up to about one centimeter in length. It is mostly found in the form of radial, rosette-shaped or kidney mineral aggregates and crusty coatings. Unharmed crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer . Its color varies from dark blue-green to almost black, and its line color is also blue-green.

Etymology and history

Close-up of clear blue, needle-like clinoclase crystals from Wheal Gorland, Cornwall, England (image width: 1.8 mm)

Klinoklas was first discovered in the "Wheal Gorland" mine near St Day in Cornwall (England) and was described in 1830 by Breithaupt , who used the Greek κλίυειυ [klinein] for tend and κλαυ [klasein, based on the fact that it was perfectly cleavable towards the base ] named for break.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the clinoclase belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the general division of "anhydrous phosphates with foreign anions ", where together with cornetite and gilmarite it was one formed an independent group.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns the Klinoclase to the class of “phosphates, arsenates and vanadates” and there to the category of “phosphates, etc. with additional anions; without H 2 O “. However, this section is now more precisely subdivided according to the size of the cations involved and the ratio between the other anions and the phosphate, arsenate or vanadate complex, so that the mineral is classified according to its composition in the sub-section “With only medium-sized cations (OH, etc.) .): RO 4  > 2: 1 “can be found, where it is the only member of the unnamed group 8.BE.20 .

The systematics of minerals according to Dana also assigns the clinoclase to the class of "phosphates, arsenates and vanadates" and there into the department of "anhydrous phosphates etc., with hydroxyl or halogen". Here he is the namesake of the "Klinoclase Group" with the system no. 41.03.01 and the other members Gilmarit and Lapeyreit can be found in the subsection of " Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 3 (XO 4 ) Z q ".

Modifications and varieties

The compound Cu 3 [(OH) 3 | AsO 4 ] is dimorphic, which means that it occurs in nature as a triclinic modification of gilmarite in addition to the monoclinic crystallizing modification clinoclase .

Education and Locations

radial needle clinoclase from the type locality St Day, Cornwall
Scaly clinoclase aggregate from the "Majuba Hill Mine", Antelope, Pershing County , Nevada, USA (size: 2.2 × 2.2 × 1.1 cm)

Klinoklas forms as a typical, albeit rare secondary mineral in the oxidation zone arsenic-rich , basic copper ore - deposits . Accompanying minerals include cornubite , cornwallite , konichalcite and olivite .

As a rather rare mineral formation, clinoclase can sometimes be abundant at different sites, but overall it is not very common. So far (as of 2010) around 110 sites are known worldwide. In addition to its type locality Wheal Gorland, Klinoklas was also found in Cornwall at Carharrack , Redruth , St Ives , in the mining area of ​​St Just and at Tavistock (Devon) .

The "Horný Bartolomej Mine" near Novoveská Huta (Vorderhütten) in Okres Spišská Nová Ves (Slovakia) and the "Majuba Hill Mine" near Antelope in Pershing County of Nevada (USA) are known due to the extraordinary finds of Klinoklas

In Germany, Klinoklas was found in the Black Forest (Baden-Württemberg), Odenwald (Hesse), Siegerland (North Rhine-Westphalia) and in the Ore Mountains (Saxony).

In Austria, the mineral has so far only been found on the Gratlspitze and on an old dump near Mockleiten near Rattenberg in Tyrol.

Other locations include Argentina, Australia, Bulgaria, Chile, China, the Democratic Republic of the Congo, France, Greece, Ireland, Italy, Japan, Morocco, Mexico, Namibia, Portugal, Zimbabwe, Slovakia, Spain, South Africa, the Czech Republic, Hungary, the United Kingdom (Great Britain) and the United States of America (USA).

Crystal structure

Clinoclase crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 7.26  Å ; b  = 6.46 Å; c  = 12.38 Å and β = 99.5 ° and 4 formula units per unit cell .

See also

literature

Web links

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

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  449 .
  2. ↑ a b c Clinoclase , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66 kB )
  3. ↑ a b c Mindat - Clinoclase
  4. ↑ Mindat - Number of locations for Klinoclase
  5. ↑ Find location list for Klinoklas in the Mineralienatlas and in Mindat