Chrysocolla

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Chrysocolla
Chrysocolla-66635.jpg
niery chrysocolla from the L'Etoile du Congo mine near Lubumbashi, Katanga, Democratic Republic of the Congo
General and classification
chemical formula Cu 4 H 4 [(OH) 8 | Si 4 O 10 ] • n H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.ED.20 ( 8th edition : VIII / E.21)
0374.03.02.01
Similar minerals Azurite , malachite , dioptase , turquoise
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol not known
Physical Properties
Mohs hardness 2 to 4
Density (g / cm 3 ) 1.93 to 2.4
Cleavage no
Break ; Tenacity shell-like, uneven
colour blue and green in different compositions and shades
Line color White
transparency translucent to opaque
shine Glass gloss, greasy gloss, earthy matt
Crystal optics
Refractive indices n α  = 1.575 to 1.585
n β  = 1.597
n γ  = 1.598 to 1.635
Birefringence δ = 0.023 to 0.050
Optical character uniaxial positive
Pleochroism colorless - pale blue-green

Chrysocolla , as Chrysokolla , Pebble copper , Kieselmalachit , copper gravel , copper green or Berggrün known is a common mineral from the mineral class of " Silicate and Germanates ". It crystallizes in the orthorhombic crystal system with the approximate chemical composition Cu 4 H 4 [(OH) 8 | Si 4 O 10 ] · n H 2 O and developed predominantly micro- crystalline , low one to traubige, stalactitic or granular to earthy mineral aggregates and crusty Overlays in a blotchy, blue-green color of various shades.

Etymology and history

Chrysocolla has been known since ancient times . The name is a combination of the Greek words χρυσός chrysos (gold) and κόλλα kolla (glue), meaning gold glue, as it was used as an aid in ancient goldsmithing, granulation .

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the chrysocolla still belongs to the division of " ring silicates (cyclosilicates)", where it forms a separate group with dioptase .

Since the complete revision of Strunz'schen systematic mineral in the 9th edition is the chrysocolla in the department of " phyllosilicates (phyllosilicates)" and there due to its crystal structure in the subsection "phyllosilicates (phyllosilicates) with kaolinite, composed of tetrahedral or octahedral networks" sorted. The mineral can be found there together with allophane , bismuth ferrite , chapmanite , imogolite and neotokite in the unnamed group 09.ED.20 .

The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns the chrysocolla to the layered silicate department, but in this system the departments are already subdivided more precisely according to the structural structure and the mineral can be found accordingly in the specific department of layered silicates with modulated layers and there in the subdivision of layered silicates: modulated layers with connected strips . Chrysocolla can be found there as the only member of the unnamed group 74.03.02

Crystal structure

Chrysocolla crystallizes orthorhombically in an unspecified space group with the lattice parameters a  = 5.72 to 5.92  Å ; b  = 17.7 to 18.0 Å and c  = 8.00 to 8.28 Å and 2 formula units per unit cell .

properties

Chrysocolla is infusible in front of the soldering tube. It dissolves in hydrochloric acid and separates out powdered SiO 2 .

Education and Locations

Stalactitic chrysocolla from the Ray Mine in Scott Mountain, Arizona, USA

Chrysocolla is a typical secondary mineral that emerges from other copper minerals through transformation (weathering, metamorphosis) . Together with azurite , malachite , cuprite and others, it is therefore mainly found in copper deposits .

Chrysocolla has so far (as of 2010) been found at more than 2,700 sites worldwide, including Broken Hill in Australia , Saida / Kreischa , Schneeberg (Saxony), Lauterberg and Kupferberg in Germany , Mednorudnyansk / Ural in the Russian Federation and Bisbee and Morenci in the USA .

use

As a raw material

In local accumulation, chrysocolla is used as copper ore . As a copper mineral, it has a toxic effect on certain living beings and is therefore used, among other things, as an anti- fouling additive for underwater paints, especially in shipbuilding .

As a gem

Mineral aggregate made of malachite and chrysocolla, polished

Chrysocolla is a popular gemstone because of its lively blue-green spotted surface . However, due to its low hardness, water retention and the tendency to crack, the stone reacts very sensitively to major warming and physical and chemical stress.

Two very similar mineral adhesions ( rocks ) are also commercially available: Chrysocolla quartz is a mixture of chrysocolla and quartz . Eilat stone is one of chrysocolla, malachite and turquoise . Another misleading trade name is Azulita for an intergrowth of chrysocolla, azurite, malachite, cuprite and dioptase.

See also

literature

Web links

Commons : Chrysocolla (Chrysocolla)  - Collection of images, videos, and audio files

Individual evidence

  1. ↑ a b Chrysocolla at mindat.org (English)
  2. ^ A b 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. 676 .
  3. ↑ Mindat - Localities for Chrysocolla