Caledonite
| Caledonite | |
|---|---|
 ( overall size: 5.4 × 3.4 × 2.3 cm ) |
|
| General and classification | |
| other names |
|
| chemical formula | Pb 5 Cu 2 [(OH) 6 | CO 3 | (SO 4 ) 3 ] |
|
Mineral class (and possibly department) |
Sulfates (and relatives) |
|
System no. to Strunz and to Dana |
7.BC.50 ( 8th edition : VI / B.09) 03.32.02.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | rhombic-pyramidal mm 2 |
| Room group (no.) | Pnm 2 1 (No. 31) |
| Lattice parameters | a = 7.15 Å ; b = 20.09 Å; c = 6.56 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2.5 to 3 |
| Density (g / cm 3 ) | measured: 5.6 to 5.76; calculated: 5.69 |
| Cleavage | perfect after {010}, imperfect after {100} and {101} |
| Break ; Tenacity | uneven; brittle |
| colour | blue to bluish green, chip green |
| Line color | light green |
| transparency | transparent to translucent |
| shine | Glass gloss, resin or fat gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.813 (3) n β = 1.866 (3) n γ = 1.909 (3) |
| Birefringence | δ = 0.091 |
| Optical character | biaxial negative |
| Axis angle | 2V = 85 ° (measured); 84 ° (calculated) |
Caledonite is a rather seldom occurring mineral from the mineral class of " sulfates ( and relatives )". It crystallizes in the orthorhombic crystal system with the composition Pb 5 Cu 2 [(OH) 6 | CO 3 | (SO 4 ) 3 ], and is thus chemically seen a lead - copper - sulfate with additional hydroxyl and carbonate - anions .
Caledonite usually develops transparent to translucent crystals with a needle-like to prismatic habit and a resin-like to glass-like sheen on the surfaces. Often, however, the crystals are also arranged in radial or tufted aggregates . The color of the mineral varies between dark chip green and lighter bluish green , while the line color is light green.
With a Mohs hardness of 2.5 to 3, caledonite is one of the medium-hard minerals that, like the reference mineral calcite (3), can be scratched with a copper coin.
Etymology and history
Caledonite was first discovered at Leadhills in southwest Scotland and described in 1820 by Henry James Brooke (1771–1857), who initially referred to the mineral as Cupreous sulphato-carbonate of lead . A year later, Karl Caesar von Leonhard adopted this name in his second edition of his work Handbuch der Oryktognosie , but translated it into German as copper-containing carbonate of sulfur .
When August Breithaupt published his “Complete Characteristics of the Mineral System” in 1832, the name of the mineral was based more on its crystal structure and described it as a Prismatic Copper Lead Spath .
The name caledonite or calédonite, which is still valid today, was finally given to the mineral by François Sulpice Beudant , who named it after the Latin-Celtic word for Scotland , based on its type locality .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the caledonite belonged to the mineral class of "sulfates, selenates, tellurates, chromates, molybdates, wolframates" and there to the department of "anhydrous sulfates with foreign anions ", where it was classified as the sole member formed the independent group VI / B.09 .
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 caledonite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and there in the department of “Sulphates (selenates etc.) with additional anions, without H 2 O”. However, this section is further subdivided according to the size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With medium-sized and large cations”, where it is also the only member of the unnamed group 7.BC.50 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns caledonite to the class of "sulfates, chromates and molybdates", which also includes the subordinate selenates, tellurates, selenites, tellurites, sulfites and chromates. Here, caledonite belongs to the “Compound Sulphates” department and is the only member of the unnamed group 32.03.02 within the subdivision “ Compound Sulphates (anhydrous) with polyanionic formula ”.
Crystal structure
Caledonite crystallizes orthorhombically in the space group Pnm 2 1 (space group no. 31) with the lattice parameters a = 7.15 Å ; b = 20.09 Å and c = 6.56 Å and 2 formula units per unit cell .
properties
Like the chemically similar minerals susannite , leadhillite and macphersonite , caledonite is foamingly soluble in nitric acid with the release of carbon dioxide . A white precipitate of lead sulfate forms .
Education and Locations
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As a typical secondary mineral, caledonite is mainly formed in the weathering zone of lead and copper deposits. Accompanying minerals include angelsite , azurite , brochantite , cerussite , leadhillite , linarite and malachite .
As a rather rare mineral formation, caledonite can in part be abundant at different sites, but overall it is not very common. Around 300 sites are known to date worldwide (as of 2011). In addition to its type locality, Leadhills, which is also known for particularly large caledonite crystals of up to 2 cm in size, the mineral occurred in the United Kingdom in many other places in England , Scotland and Wales .
The “Mammoth Mine” in Pinal County (Arizona) and the “Blue Bell Mine” in San Bernardino County (California) in the USA, where crystals between 1.5 and 2 cm in size have been found, are known for their extraordinary caledonite finds were. Besides are from the Tchah-Mille -Mine at Anarak in the Iranian province of Esfahan still Druse finds with well-developed crystals known.
In Germany, caledonite has been found mainly in the Black Forest in Baden-Württemberg, but also at Hohenstein near Lautertal and in the "Grube Vereinigung" near Eisenbach in Hesse, in several places in the Harz Mountains from Lower Saxony to Saxony-Anhalt, in several pits in the Bergisch region Landes , Ruhr area , Sauerland and Siegerlandes in North Rhine-Westphalia, in several places in the Eifel and in the Westerwald in Rhineland-Palatinate and in the "Holy Trinity" pit near Zschopau in Saxony.
In Austria, several sites in Carinthia , Lower Austria , Salzburg and Styria are known, in Switzerland, however, so far only the "Les Moulins Mine" near Saint-Luc VS in the canton of Valais.
Other locations are in Argentina, Australia, Belgium, Bolivia, Bulgaria, Chile, China, France, Greece, Ireland, Italy, Japan, Canada, Morocco, Mexico, Namibia, Norway, Pakistan, Portugal, Romania, Russia, Spain, South Africa and the United States of America.
See also
literature
- Charles Palache, WE Richmond: Caledonite , in: American Mineralogist , Volume 24 (1939) ( PDF 182.5 kB )
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 602 (first edition: 1891).
Web links
- Mineral Atlas: Caledonite (Wiki)
Individual evidence
- ↑ 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. 375 .
- ↑ Webmineral - Caledonite
- ↑ a b John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Caledonite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.9 kB )
- ↑ a b c d Mindat - Caledonite
- ^ HJ Brooke: Abt. XXI - Account of Three New Species of Lead-Ore found at Leadhills , in: The Edinburgh philosophical journal , Volume 3, Edinburgh 1820 in the Google book search
- ^ Carl Caesar von Leonhard: Handbuch der Oryktognosie , 2nd edition, published by JCB Mohr, Heidelberg 1826, pp. 254-255 in the Google book search
- ↑ August Breithaupt: Complete characteristics of the mineral system , 3rd edition, Arnoldische Buchhandlung, Dresden and Leipzig 1832, p. 53 in the Google book search
- ↑ FS Beudant: Calédonite , in: Traité Élémentaire de Minéralogie , 2nd Edition, Paris 1832, pp. 367–369 ( PDF 129.9 kB )
- ^ A b Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 142 ( Dörfler Natur ).
- ↑ Mindat - Localities for Caledonite