Euchroit

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Euchroit
Euchroite-242668.jpg
Euchroit stage from the Svätodušná valley near Ľubietová , Slovakia
(size: 2.0 × 1.9 × 0.8 cm)
General and classification
chemical formula Cu 2 [OH | AsO 4 ] • 3H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DC.07 ( 8th edition : VII / D.07)
42.06.03.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-disphenoidic; 222
Room group (no.) P 2 1 2 1 2 1 (No. 19)
Lattice parameters a  = 10.06  Å ; b  = 10.51 Å; c  = 6.10 Å
Formula units Z  = 4
Frequent crystal faces {010}, {100}, {110}, {101}, {0kl}, {h0l}, striped parallel [010]
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 3.44; calculated: 3.47
Cleavage indistinct after {101} and {110}
Break ; Tenacity uneven to slightly scalloped; brittle
colour emerald green to leek green, bluish green in transmitted light
Line color light green
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.695
n β  = 1.698
n γ  = 1.733
Birefringence δ = 0.038
Optical character biaxial positive
Axis angle 2V = 28 to 30 ° (measured); 34 ° (calculated)

Euchroit is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition Cu 2 [OH | AsO 4 ] · 3H 2 O, so from a chemical point of view it is a water-containing copper arsenate with additional hydroxide ions .

Euchroit is transparent to translucent and develops predominantly idiomorphic crystals with a thick tabular, isometric or prismatic habit of emerald green to leek green with light green streak color . The crystal surfaces show a glass-like sheen .

With a Mohs hardness of 3.5 to 4, Euchroit lies between the reference minerals calcite (3) and fluorite (4), so it can be easily scratched with a pocket knife .

Etymology and history

Euchroit was first discovered by Herr von Heldreich in the copper deposit Svätodušná ( Svätoduska ) near Ľubietová (German Libethen ) in Okres Banská Bystrica, Slovakia, and described in 1823 by August Breithaupt , who named the mineral because of its emerald green color after the Greek words εὐ eu d. H. 'Good, beautiful' and χρῶμα chrṓma d. H. Named 'color'.

The type material of the mineral is kept in the mineralogical collection of the Technical University Bergakademie Freiberg (register no. 21335).

classification

In the meanwhile outdated, but still in use, 8th edition of the mineral systematics according to Strunz , the Euchroit belonged to the division of "Water-containing phosphates with foreign anions ", where together with cloncurryite , legrandite , nevadaite , nissonite , spencerite and strashimirite, it forms the unnamed group VII / D .07 made.

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 the Euchroit to the department of “Phosphates etc. with additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  = 1: 1 and <2: 1 “can be found where it is the only member of the unnamed group 8.DC.07 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Euchroit to the class of "phosphates, arsenates and vanadates" and there in the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is to be found as the only member of the unnamed group 06/42/03 within the sub-section " Hydrogen phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q × x (H 2 O) ".

Education and Locations

Euchroit from the "Cramer Creek" copper deposit, Missoula County , Montana, USA (size: 3.5 × 2.2 × 0.5 cm)

Euchroit forms in the oxidation zone of some copper-bearing hydrothermal deposits . As Begleitminerale occur among other azurite , malachite , Olivenit and Strashimirit on.

As a rare mineral formation, Euchroit could only be proven at a few localities, whereby so far (as of 2013) around 20 localities are known. In addition to its type locality Svätodušná ( Svätoduska ) near Ľubietová, the mineral has only appeared in Slovakia in the Farbište deposit near Poniky . The Slovak sites, together with the "Mina de Carlés" in the Spanish municipality of Salas (Asturias), are among the best-known sites for this mineral due to their abundant Euchroit finds.

The only known German site to date is the “Grube Grüneau” (Grube Au, Grünau) near Schutzbach in Rhineland-Palatinate.

In Austria, Euchroit was found in a magnesite pit, the “Danielstollen” in the Schwarzleo district and a prehistoric dump on the Schwarzleograben near Hütten (municipality of Leogang) in Salzburg and on the Graschberg and the Flirscher Skihütte in North Tyrol .

In Switzerland, the Mürtschenalp in the Murgtal (St. Gallen) is also only one known place of discovery for Euchroit so far.

Other sites include the "Nadbuck Mine" near Silverton (New South Wales) and the "Dome Rock Copper Mine" in South Australia in Australia, the Zapachitsa copper deposit (Zapacica) in the Bulgarian municipality of Swoge ; near Sierra Gorda in the Chilean Región de Antofagasta , the mines of "Kamariza" near Aghios Konstantinos (Kamariza) in the Greek municipality of Lavrio (Attica), the mines of Montevecchio in the municipality of Arbus (Sardinia) in Italy, Moldova Nouă in Romania, Horní Slavkov ( Schlaggenwald ) in the Czech region of Karlovarský kraj ( Karlsbad ) as well as the “Copper Cliff Mine” in Missoula County (Montana), the “Number Eight Mine” ( Blue Star Mine ) in Eureka County (Nevada) and the “Sterling Mine” “On Sterling Hill in Sussex County, New Jersey in the United States of America.

Crystal structure

Euchroit crystallizes orthorhombically in the space group P 2 1 2 1 2 1 (space group no. 19) with the lattice parameters a  = 10.06  Å ; b  = 10.51 Å and c  = 6.10 Å and 4 formula units per unit cell .

See also

literature

Web links

Commons : Euchroite  - 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.  497 .
  2. ↑ Webmineral - Euchroite
  3. ↑ a b c Euchroite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.5 kB )
  4. ↑ a b c Mindat - Euchroite
  5. ↑ Mindat - Number of locations for Euchroit
  6. ↑ Find location list for Euchroit in the Mineralienatlas and Mindat