Cuprite

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Cuprite
Cuprite.jpg
Cuprite with malachite from the Dikuluwe Mine, Kolwesi, Katanga (Shaba), Democratic Republic of the Congo
General and classification
chemical formula Cu 2 O
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.AA.10 ( 8th edition : IV / A.02)
01/04/01/01
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Pn 3 m (No. 224)Template: room group / 224
Lattice parameters a  = 4.2685  Å
Formula units Z  = 2
Frequent crystal faces (111), (110), (100), (112), (221), (210), (223)
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) 6.14 to 6.15
Cleavage indistinct after {111}
Break ; Tenacity uneven to scalloped
colour orange, orange-red to brownish-red, gray to black
Line color brownish red
transparency transparent to opaque
shine Diamond luster, metallic luster, earthy
Crystal optics
Refractive indices n α  = 2.85

Cuprite (outdated red copper ore , chemically copper (I) oxide ) is a rather seldom occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the cubic crystal system with the chemical composition Cu 2 O and usually develops different combinations of cubic crystal forms such as octahedron , rhombic dodecahedron and rarely also cubes , but also needle-like or granular to massive mineral aggregates from orange-red to almost black color.

Etymology and history

The cuprite was scientifically described for the first time in 1845 by Wilhelm Ritter von Haidinger , who named the mineral because of its copper content with reference to the Latin name for copper cuprum . The Romans called the ore aes cyprium (ore from Cyprus).

classification

In the meanwhile outdated system of minerals according to Strunz (8th edition) , the cuprite still belongs to the general division of "oxides with (the approximate molar ratio ) metal: oxygen = 2: 1 and 1: 1". Since the revision of Strunz's mineral system in the 9th edition , this section has been more precisely subdivided according to the exact molar ratio and the size of the cations involved and the mineral can be found accordingly in the sub-section of "Oxides with the molar ratio metal: oxygen = 2: 1 (and 1.8: 1) ".

The more common systematics of minerals according to Dana in the English-speaking world places the cuprite in the division of " Simple oxides with a cation charge of 1 + and the general formula A 2 O ".

Crystal structure

Crystal structure of cuprite

Cuprite crystallizes cubically in the space group Pn 3 m (space group no. 224) with the lattice parameter a  = 4.2685  Å and two formula units per unit cell . Template: room group / 224

Two structures made of [OCu 4 ] tetrahedra placed one inside the other , which have no chemical bond to one another, form the basic structure of cuprite, which is also known as the “double anti- cristobalite structure ”.

properties

Cuprite has a Mohs hardness of 3.5 to 4, so it belongs to the soft minerals. It is soluble in acids and ammonia . The mineral can turn dark gray when exposed to light.

Modifications and varieties

Chalcotrichite
  • Chalcotrichite or copper blossom is a variant of the shape with needle-like to hair-like crystals according to [001].
  • As Kupferziegelerz or short Ziegelerz firstly the massive up earthy varieties of Cuprits and on the other a red-brown mixture of cuprite and other copper minerals with limonite referred.

Education and Locations

Pseudomorphosis (perimorphosis) from malachite to cuprite

Cuprite is a typical secondary mineral that is formed by oxidation from various copper sulfides or native copper and occurs primarily in the reduction zone of copper-containing, sulfidic ore bodies . Accompanying minerals are mainly solid copper , azurite and malachite , but also antlerite , atacamite , brochantite , calcite , chrysocolla and tenorite . It is often found overgrown with malachite in the form of perimorphoses .

So far, cuprite has been found at over 2000 sites worldwide (as of 2009). The countries Argentina , Australia , Bolivia , Chile , China , Germany , France , Italy , Canada , Mexico , Namibia , Norway , Austria , Peru , Russia , Sweden , Spain , the United Kingdom (Great Britain) and the United States (USA).

Well to perfectly developed crystals emerged mainly in the African deposits of Tsumeb (Namibia) and Shaba (today Katanga ). Crystals up to 15 cm in size overgrown with malachite were found in Onganja (Namibia). A group of crystals measuring 3.1 cm in size was also found in Cornwall .

use

As a raw material

Cuprite is widespread as a mineral and was already mined in antiquity because of its considerable copper content of 88.8%, but the mineral only occasionally occurs locally in such a way that mining as copper ore is economically worthwhile. The mineral can easily release considerable amounts of copper by simply melting it, which means that a lot of copper is extracted.

As a gem

For commercial use as a gem stone , the cuprite is too soft due to its low hardness and also too sensitive even to light acids such as sweat. It would therefore be damaged too easily as a finger or arm jewelry and generally attacked too quickly when worn. Its bright red color with good quality and its strong shine make it an interesting and coveted stone for collectors and hobby cutters, which is often sold or exchanged in faceted form .

See also

literature

Web links

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

Individual evidence

  1. ↑ a b c d Webmineral - Cuprite (English)
  2. ↑ a b c American Mineralogist Crystal Structure Database - Cuprite (English, 1990)
  3. ^ Ronald Bonewitz: Stones & Minerals: [Rocks, minerals, precious stones, fossils] . Dorling Kindersley, Munich 2009, ISBN 978-3-8310-1469-9 .
  4. ↑ a b Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin, Heidelberg, New York 2005, ISBN 3-540-23812-3 , pp. 50 .
  5. ↑ List of localities for cuprite in the Mineralienatlas and in Mindat - Localities for Cuprite
  6. ^ Walter Schumann: Precious stones and gemstones . 13th edition. BLV, Munich 2002, ISBN 3-405-16332-3 , p. 222 .
  7. ^ Precious stone etiquette from Prof. Leopold Rössler - Cuprite