Bromargyrite
| Bromargyrite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | AgBr |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.AA.15 ( 8th edition : III / A.02) 01/09/04/02 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | m-3m |
| Space group | Fm 3 m (No. 225) |
| Lattice parameters | a = 4.77 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {111}, {011} |
| Twinning | seldom along {111} |
| Physical Properties | |
| Mohs hardness | 1.5 to 2.5 (average 2) |
| Density (g / cm 3 ) | measured: 6.474; calculated: 6.477 |
| Cleavage | is missing |
| Break ; Tenacity | uneven to slightly scalloped |
| colour | light yellow, olive green, greenish brown, greenish gray to yellowish gray |
| Line color | white to yellowish white |
| transparency | transparent to translucent |
| shine | Diamond gloss, resin gloss to wax gloss |
| Crystal optics | |
| Refractive index | n = 2.253 |
| Birefringence | none, as isotropic |
Bromargyrite , also known as bromite , silver bromide , brom spar or bromyrite , is a rather seldom occurring mineral from the mineral class of halides . It crystallizes in the cubic crystal system with the chemical composition AgBr .
Bromargyrite is transparent to translucent and develops cubic crystals up to one centimeter in size with a diamond-like sheen on the surfaces, which are arranged in parallel groups. It is also often found in the form of coarse masses or waxy to horn-like, crusty coatings. The color of the mineral varies between light yellow and olive green, often with a brownish or gray cast.
Special properties
When exposed to light, the mineral turns brown or black due to the formation of elemental silver . Bromargyrite can give off a strong odor of "medicinal products" in the air.
With an average Mohs hardness of 2, bromargyrite is one of the soft minerals that, like the reference minerals plaster of paris or halite, can be scratched with the fingernail. In contrast to these rather brittle minerals, bromargyrite is extremely malleable and can be cut with a knife.
Bromargyrite is easily meltable in front of the soldering tube . It hardly dissolves in acids, but it does in ammonia .
Etymology and history
The mineral was named after its composition, the elements bromine and silver (Greek ἄργυρος [argyros] and Latin argentum).
Bromargyrite was first discovered by Pierre Berthier near Plateros in the Mexican state of Zacatecas . The miners there called this silver ore Plata verde (German: green silver).
The mineral was scientifically described and named in 1849 by August Breithaupt (the analysis was carried out by Carl Friedrich Plattner ).
classification
In the now outdated, but still in use 8th edition of the mineral systematics according to Strunz , the bromargyrite belonged to the general department of the "simple halides", where together with carobbiite , chlorargyrite , halite , sylvite and villiaumite, the "halite series" with the system No. III / A.02 .
The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies bromogyrite in the more finely subdivided division of “simple halides without H 2 O”. This is further subdivided according to the molar ratio of metal (M) to the halogen (X) associated with it , so that the mineral can be found in the sub-section "M: X = 1: 1 and 2: 3" according to its composition, where there is only the "Chlorargyrite group" with the system no. 3.AA.15 forms.
The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , assigns bromargyrite to the class / division of "halides". Here it is together with chlorogyrite and embolite in the "embolite group" with system no. 09.01.04 to be found in the subsection of " Anhydrous and water-containing halides with the formula AX ".
Crystal structure
Bromargyrite crystallizes in the cubic crystal system in the space group Fm 3 m (space group no. 225) with the lattice parameter a = 4.77 Å and four formula units per unit cell .
Modifications and varieties
Bromogyrite (AgBr) forms a seamless mixed series with chlorine argyrite (AgCl), the links or mixed crystals of which are referred to as bromochloroargyrite or embolite (Ag (Br, Cl)). Boron and iodine containing bromine argyrite is also very common. Iodine-containing embolite is also known as iodobromite (Ag (Br, Cl, I)).
Education and Locations
Bromargyrite is found as a secondary mineral mainly in the oxidation zone of silver deposits and forms particularly under arid , i.e. dry, climatic conditions. In addition to native silver among other things still occur Jodargyrit , Smithsonite and various iron - manganese oxides as Begleitminerale on.
As a rather rare mineral formation, bromargyrite can sometimes be abundantly present at various sites, but overall it is not very common. A little more than 200 sites are known to date (as of 2012). In addition to its type locality Plateros, the mineral occurred in many other pits in Zacatecas and other states of Mexico.
In Germany, bromargyrite was found in the “ Clara ” and “Fortuna” mines near Oberwolfach in Baden-Württemberg, near Bad Ems and in the “Schöne Aussicht” mine near Dernbach in Rhineland-Palatinate, in the Mansfeld Basin in Saxony-Anhalt and in the "Sauberg" mine near Ehrenfriedersdorf in the Saxon Ore Mountains.
Other sites are in Argentina, Australia, Bolivia, Chile, China, France, Italy, Morocco, New Zealand, Russia, Spain, the Czech Republic, Hungary, the US Virgin Islands and in the United States of America.
use
Bromargyrite is an ore used to extract elemental silver.
See also
literature
- JFA Breithaupt, CF Plattner: Determination of new minerals: embolite or bromochlorosilver . In: Annals of Physics and Chemistry . tape 153 , 1849, pp. 134–135 ( rruff.info [PDF; 127 kB ; accessed on November 26, 2018]).
Web links
- Mineral Atlas: Bromargyrite
- Database-of-Raman-spectroscopy - list of results from analyzes of various bromogyrite samples
Individual evidence
- ^ A b c 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. 149 .
- ↑ a b c d Bromargyrite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 60 kB ; accessed on November 26, 2018]).
- ^ A b c d Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 320 .
- ↑ a b Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 367 .
- ↑ Mindat - Bromargyrite (English)
- ↑ a b CF Rammelsberg: Handbuch der Mineralchemie . Verlag von Wilhelm Engelmann, Leipzig 1860, p. 196 ( available online at archive.org - Internet Archive ).
- ↑ JFA Breithaupt, CF Plattner: Determination of new minerals: embolite or bromochlorosilver . In: Annals of Physics and Chemistry . tape 153 , 1849, pp. 134–135 ( rruff.info [PDF; 127 kB ; accessed on November 26, 2018]).
- ↑ Mindat - Number of localities for Bromargyrite (English)
- ↑ Find location list for bromargyrite at the Mineralienatlas and at Mindat