Oliveite

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Oliveite
Oliveite - Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany.jpg
Oliveite (crystal size: 1 mm) from the Clara pit near Oberwolfach in the Black Forest
General and classification
other names
  • Arsenic acid copper ore
  • Olive copper
  • Olive ore
chemical formula Cu 2 [OH | AsO 4 ]
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.BB.30 ( 8th edition : VII / B.06)
41.06.06.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) P 2 1 / n (No. 14)
Lattice parameters a  = 8.5844  Å ; b  = 8.2084 Å; c  = 5.9258 Å
β  = 90.13 °
Formula units Z  = 4
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) measured: 4.46; calculated: 4.45
Cleavage indistinct after {101} and {110}
Break ; Tenacity shell-like to uneven
colour olive-green, greenish-brown to brown, gray-green to gray, gray-white, straw-yellow in fibrous formation
Line color light green
transparency translucent to opaque
shine Diamond gloss, glass gloss, pearlescent to silk gloss
Crystal optics
Refractive indices n α  = 1.747 to 1.780
n β  = 1.788 to 1.820
n γ  = 1.829 to 1.865
Birefringence δ = 0.082 to 0.085
Optical character alternating biaxially
Axis angle 2V = measured: 80 to 90 °; calculated: 46 to 84 °

Olivenit , as arsenate copper ore , Olivenerz , olive copper or Pharmacochalcit known is a mineral from the mineral class of " phosphates , arsenates and vanadates ," which can be abundant in various localities in part, but altogether not widespread. It crystallizes in the monoclinic crystal system with the composition Cu 2 [OH | AsO 4 ], so from a chemical point of view it is a copper arsenate with hydroxide ions as additional anions .

Oliveite usually develops short to long prismatic crystals , but also needle-like, radial-rayed or massive mineral aggregates of olive-green, greenish-brown to brown, gray-green to gray or gray-white color. In fibrous form, oliveite can also take on a straw yellow color. The line color , on the other hand, is always light green.

The surfaces of the translucent to opaque crystal surfaces have a gloss that is roughly between that of cut diamonds and glass. Fibrous aggregates, on the other hand, have a similar pearlescent or silk gloss shimmer. With a Mohs hardness of 3, oliveite is still one of the soft minerals that, like the reference mineral calcite, can be scratched with a copper coin.

With Adamin (Zn 2 [OH | AsO 4 ]), olivite forms a complete mixed crystal row .

Etymology and history

Straw yellow olivite in needle-like, radial-rayed formation from the type locality "Carharrack Mine" (field of view approx. 1 × 0.7 mm)

Oliveite was first discovered in the "Carharrack Mine" near Gwennap in the English county of Cornwall (United Kingdom).

The mineral was first analyzed and described in 1786 by Martin Heinrich Klaproth , who initially referred to it as arsenic acid copper ore . Even Abraham Gottlob Werner described the "Cornish" derived mineral 1789 and gave him the name Olivenerz often based on its characteristic olive green color of the fruit of the same name like the immature stage.

The name of the oliveite, which is still valid today, was not given until 1820 by Robert Jameson , who internationalized the name chosen by Werner.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the olivite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates with foreign anions ", where it belonged together with Adamin , Eveit , Libethenit , Paradamin , Tarbuttit and Zincolibethenit the independent group of "Libethenite series" formed.

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 olivite to the class of “phosphates, arsenates and vanadates” and there to the department of “phosphates, etc. with additional anions ; without H 2 O “. However, this section is further subdivided according to the size of the cations involved and the ratio of the additional anions to the phosphate, arsenate or vanadate complex, so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  ≤ 1: 1 “can be found, where together with Adamin, Auriacusit , Eveit, Libethenit, Zinkolibethenit and Zinkolivenit the“ Libethenitgruppe ”with the system no. 8.BB.30 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the olivite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates etc., with hydroxyl or halogen". Here he is the namesake of the " olivite group " with the system no. 41.06.06 and the other members Libethenit, Adamin, Eveit, Zincolibethenit and Zinkolivenit can be found in the subsection "Anhydrous phosphates etc., with hydroxyl or halogen with (A) 2 (XO 4 ) Z q ".

Crystal structure

Oliveite crystallizes monoclinically in the space group P 2 1 / n (space group no. 14) with the lattice parameters a  = 8.5844  Å ; b  = 8.2084 Å; c  = 5.9258 Å and β = 90.13 ° as well as 4 formula units per unit cell .

properties

In front of the soldering tube , Olivent changes color and melts slightly, with the sample bulging strongly and giving off toxic arsenic vapors .

Education and Locations

Oliveite (black green) and fragranceite (light green) from the Tsumeb Mine, Namibia (size: 5.6 × 3.3 × 2.1 cm)

Olivenit forms as secondary copper arsenate in the oxidation zone of hydrothermal copper - deposits . Accompanying minerals include azurite , brochantite , chalcophyllite , chrysocolla , cornetite , cornwallite , clinoclase , konichalcite , malachite , metazeunerite , pharmacosiderite , scorodite , spangolite and tirolite .

In total, oliveite has so far (status: 2011) been found at around 450 sites. In addition to its type locality "Carharrack Mine" near Gwennap, the mineral occurred in the United Kingdom (Great Britain) in many other places and mines in the county of Cornwall, including Callington , Gunnislake , Camborne , Illogan , Redruth , Liskeard , St Hilary , St Austell , St Just in Penwith and Wadebridge . Other sites in England are in Cheshire , Cumbria , Devon and Leicestershire . Oliveite was also found at Leadhills in Scotland and in Ceredigion and Powys in Wales.

In Germany, Olivenit occurred mainly in the Black Forest and Odenwald in Baden-Württemberg; at Rudolfstein in the Spessart in Bavaria; at Hohenstein , near Richelsdorf and Altenmittlau in Hesse; in several places in the Harz Mountains from Lower Saxony to Thuringia; in the Bergisches Land , in the Eifel , near Heiligenhaus and in the Sauerland and Siegerland in North Rhine-Westphalia; near Imsbach , Frücht and in the Westerwald in Rhineland-Palatinate; near St. Barbara (Wallerfangen) in Saarland; in the Ore Mountains and Vogtland in Saxony as well as in Bad Lobenstein , Gera and Stempeda in Thuringia.

In Austria, the mineral was found in the Karawanken in Carinthia, in the Schwarzleograben in the Salzburg municipality of Leogang , in the copper deposit in the Styrian municipality of Flatschach and in several places in northern Tyrol .

In Switzerland, oliveite has so far been found on Mürtschenalp in the Murg Valley in the canton of Glarus; on the Tieftobel in the municipality of Schmitten GR and in the Engadin in the canton of Graubünden; near Alto Malcantone (Breno TI) in the canton of Ticino and in the communes of Martigny , Isérables and Siders (Granges VS) in the canton of Valais.

Worth mentioning due to the extraordinary oliveite finds are, among others, Wheal Gorland in Cornwall and Tavistock in Devon, where perfectly formed crystals with a diameter of up to one centimeter emerged.

Other locations are Argentina , Australia , Belgium , Bolivia , Brazil , Bulgaria , Chile , China , France , Greece , Ireland , Italy , Japan , Kyrgyzstan , Morocco , Mexico , Namibia , Poland , Portugal , Zimbabwe , Slovakia , Spain , South Africa , Taiwan , Czech Republic , Hungary and the United States of America (USA).

See also

literature

Web links

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

Individual evidence

  1. ^ 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.  444 .
  2. ↑ a b c Webmineral - Olivenite (English)
  3. ↑ a b c C. Li, H. Yang, RT Downs: Redetermination of olivenite from an untwinned single-crystal , in: Acta Crystallographica E64 (2008) i60-i61
  4. ↑ a b Olivenite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64 kB )
  5. ↑ a b c d Mindat - Olivenite (English)
  6. ^ Mindat - Arsenic acid copper ore according to Klaproth (1786) Writings of the Society of Friends of Nature Research in Berlin: 7: 160
  7. ↑ Mindat - Localities for OLIVENITE