Spangolite

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Spangolite
Spangolite-283007.jpg
Spangolite from the Blanchard Mine, Bingham , Socorro County , New Mexico, USA (image width 2.5 mm)
General and classification
chemical formula Cu 6 Al [Cl | (OH) 12 | SO 4 ] • 3H 2 O
Mineral class
(and possibly department) 		Sulfates (including selenates, tellurates, chromates, molybdates, and tungstates)
System no. to Strunz
and to Dana 		7.DD.15 ( 8th edition : VI / D.08)
01/31/05/01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-pyramidal; 3 m
Space group P 31 c (No. 159)Template: room group / 159
Lattice parameters a  = 8.25  Å ; c  = 14.35 Å
Formula units Z  = 2
Frequent crystal faces {000 1 }, {10 1 0}, {01 1 0}, {10 1 1}, {01 1 1}
Twinning Contact twins after {0001}
Physical Properties
Mohs hardness 2 after {0001}, 3 on the inclined planes
Density (g / cm 3 ) measured: 3.135 to 3.141; calculated: 3.14
Cleavage completely after {0001}, clearly after {10 1 1} and {01 1 1}
Break ; Tenacity clamshell; brittle
colour blue-green, light to dark green, emerald green
Line color light green
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.694
n ε  = 1.641
Birefringence δ = 0.053
Optical character uniaxial negative
Pleochroism weak: ω = green; ε = bluish green
Other properties
Special features Pyroelectricity

Spangolite is a rarely occurring mineral belonging to the mineral class of sulfates (and relatives). It crystallizes in the trigonal crystal system with the chemical composition Cu 6 Al [Cl | (OH) 12 | SO 4 ] · 3H 2 O and is therefore chemically a water-containing copper - aluminum sulfate with additional chlorine and hydroxide ions .

Spangolite develops blue to emerald green, hemimorphic pyramidal or tabular to isometric crystals . Massive units are also known.

Etymology and history

The name of the mineral is made up of the surname of the US mineral collector Norman Spang (1841-1922) and the Greek λίθος lithos , "stone". The mineralogist Samuel Lewis Penfield described the newly discovered mineral in 1890 and honored Spang in this way after he had sold his vast private collection of mineral finds with an estimated 5,000 to 6,000 individual pieces to the American Museum of Natural History in New York for a small sum of $ 10,000 .

The first place of discovery ( type locality ) of the mineral could never be exactly clarified. Norman Spang mineral earned by a man near Tombstone ( Cochise County lived) in the south of the US state of Arizona in the United States and its mineral samples collected within a radius of about 200 miles around the site.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the spangolite belonged to the mineral class of "sulfates, chromates, molybdates and tungstates" (including some selenates and tellurates) and there to the department of "hydrous sulfates with foreign anions " where he together with Bechererite , Camérolait , Carbonatcyanotrichit , Carrboydit , Chalkoalumit , Cyanotrichit , Glaukokerinit , Hydrombobomkulit , Hydrowoodwardit , Kyrgyzstanit , Mbobomkulit , Nickelalumit , Woodwardite , Zincowoodwardit and Zinkaluminit the "Cyanotrichit group" with the system number. VI / D.08 .

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 classifies spangolite in the category of "sulfates (selenates, etc.) with additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved and the crystal structure, so that the mineral is classified in the sub-section “With only medium-sized cations; Layers of edge-sharing octahedra "can be found, where it is the only member of the unnamed group 7.DD.15 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the spangolite to the class of "sulfates, chromates and molybdates (including selenates, tellurates, selenites, tellurites and sulfites)" and there in the category of "water-containing sulfates with hydroxyl or halogen " a. Here he is the only member of the unnamed group 01/31/05 within the subdivision "Water-containing sulfates with hydroxyl or halogen and (A + B 2+ ) m (XO 4 ) p Z q × x (H 2 O), with m: p> 6: 1 “.

Crystal structure

Spangolite crystallizes trigonal in the non- centrosymmetric space group P 31 c (space group no. 159) with the lattice parameters a  = 8.25  Å and c = 14.35 Å as well as two formula units per unit cell . Template: room group / 159

properties

Spangolite is pyroelectric , so it reacts with charge separation when the temperature changes. When the temperature rises, the crystal charges in the direction of the crystallographic c-axis, i.e. along the polar three-fold axis of rotation (“3”), positively at one end and negatively at the other. When the temperature drops, it also charges up, but the positive and negative ends are then reversed. This effect can occur with spangolite due to the non-centrosymmetric crystal class 3 m .

Education and Locations

Spangolith forms as a secondary mineral hydrothermally in the oxidation zone of copper - deposits . Accompanying minerals ( parageneses ) of spangolite are therefore typically also copper-containing such as aurichalcite , azurite , brochantite , caledonite , chalcophyllite , chrysocolla , connellite , cuprite , cyanotrichite , clinoclase , linarite , malachite , olivite , tirolite and parnauite .

As a rare mineral formation, spangolite could only be detected at a few sites, whereby so far (as of 2015) around 100 sites are known.

In Germany, spangolite was found at Freiamt (Black Forest) in Baden-Württemberg, on a slag dump near Richelsdorf in Hesse, in the Glücksrad mine near Oberschulenberg and the slag fields near Goslar in Lower Saxony, at several locations near Meschede , Müsen and Wilnsdorf in North Rhine-Westphalia. Westphalia, found near Niederfischbach in Rhineland-Palatinate, near Sadisdorf in Saxony and on the north coast of Heligoland in Schleswig-Holstein.

In Austria, the mineral has so far only been found on slag heaps near Waitschach in Carinthia and on Severinggraben near Johnsbach in Styria as well as on the north side of the Hohe Sonnblick in Salzburg and in a few places in the area around Brixlegg and Rattenberg in Tyrol.

Other localities include Australia, Chile, the Democratic Republic of the Congo (Zaire), Greece, France, Italy, Japan, Canada, Kazakhstan, Mexico, Portugal, Spain, the United Kingdom, and the United States.

See also

literature

Web links

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

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  401 .
  2. ↑ Webmineral - Spangolite. (English)
  3. ↑ a b c d e Spangolite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF; 67.1 kB).
  4. ↑ a b c d Mindat - Spangolite. (English).
  5. ^ SL Penfield - Spangolite, a new copper mineral. In: The American journal of science. P. 374 ( biodiversitylibrary.org accessed April 8, 2015).
  6. ↑ The Mineralogical Record - Charles Spang and the genesis of the naming of the mineral spangolite in honor of his son Norman Spang in 1890.
  7. ^ HA Miers: Spangolite. In: Mineralogical Magazine. Volume 10 (1894), pp. 273-277 ( minersoc.org PDF; 219 kB).
  8. ↑ Find location list for spangolite in the Mineralienatlas and Mindat .