Chlorogyrite
| Chlorogyrite | |
|---|---|
 ( total size of the step: 5.9 cm × 3.5 cm × 3.0 cm) |
|
| General and classification | |
| other names |
|
| chemical formula | AgCl |
|
Mineral class (and possibly department) |
Halides |
|
System no. to Strunz and to Dana |
3.AA.15 ( 8th edition : III / A.02) 01/09/04/01 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | Fm 3 m (No. 225) |
| Lattice parameters | a = 5.55 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {100}, {111}, {110} |
| Twinning | after {111} |
| Physical Properties | |
| Mohs hardness | 1.5 to 2 |
| Density (g / cm 3 ) | measured: 5.556; calculated: 5.57 |
| Cleavage | no |
| Break ; Tenacity | uneven to scalloped |
| colour | colorless, gray-yellow, brown-black |
| Line color | white to pearl gray |
| transparency | transparent to translucent |
| shine | When fresh, fat to diamond shine, soon becoming matt |
| Crystal optics | |
| Refractive index | n = 2.071 |
Chlorargyrite (also chlorosilver ) is a frequently occurring mineral from the mineral class of " halides " with the chemical composition AgCl and is therefore chemically silver chloride .
Chlorargyrite crystallizes in the cubic crystal system , but rarely develops small, cubic crystals and combinations as well as twins after the octahedron surface. It is mostly found in the form of massive mineral aggregates or crusty coatings. In its pure form, the mineral is colorless and transparent. However, due to foreign admixtures , it often takes on a light yellow to gray-yellow color with a tinge of purple, brownish or brownish-green, whereby the transparency decreases accordingly. However, its line color is always white to pearl gray. When fresh, chlorargyrite has a fat to diamond-like sheen , which, however, gradually becomes matt as a result of weathering.
With a Mohs hardness of 1.5 to 2, chlorine argyrite, like the reference minerals talc (1) and gypsum (2), is one of the soft minerals that can be scratched with a fingernail.
Etymology and history
Chlorargyrite was already known in the 16th century as horn silver , silver horn ore for short , as it mostly resembled horn soaked in fat and thus become transparent . A first mention without further description can be found in the works of Georgius Agricola 1530 ( Bermannus, sive de re metallica ) and his main work 1546 ( De Natura Fossilium ), where the mineral is silver ores with the designation Argentum rude purpureum or Argentum rude jecoris coloris (liver-colored silver ore) is assigned.
A more precise description of the mineral has only come down to us through Johannes Mathesius and his Sermons on the Mount, which he wrote between 1552 and 1562:
"" On the Marienberg is broken horn-colored silver / which is transparent / and melts over a light. In the fewer, however, there is a lot of white silver outside / one that becomes smoother silver from one gang / than from the other. ""
such as
"" Glaßertz but vnd dignified white silver / and what you can tell more recently on Marienberg / is transparent like a horn in a lantern / and melts vberm lies / there is what there should be. ""
indicate here a transparent, horn-colored silver ore from Marienberg in the Ore Mountains , which can be assigned to the properties of chlorine argyrite.
Another clear description of chlorargyrite is provided by Johannes Kentmann and Georg Fabricius in 1565 , summarized in a textbook by Conrad Gessner and Georg Fabricius, who also call the mineral “transparent horny silver” ( Argentum, Flavi coloris ) or “Läberfarben” ( Argentum iecoris colore ) from Marienberg in the Ore Mountains. This location is therefore also considered a type locality .
In later sources, chlorargyrit can be found under various synonyms, such as Hornerz ( Werner , 1789), Hornsilber ( Hausmann , 1813) and Silberhornz ( Leonhard , 1821) as well as its Greek derivatives κέρας [kéras] for horn and ἄργυρος [argyros] for silver as Kérargyre ( Beudant , 1832), Kerat ( Haidinger , 1845), Kerargyrite and Cerargyrite ( Dana , 1855 and 1868).
The name of the mineral, which is still valid today, is chlorine argyrite, based on its composition, chlorine on the one hand and the Greek word for silver (argyros) on the other hand, it was finally given by Albin Weisbach in 1875 , whereby Carl Friedrich Naumann in 1828 also gave it a purely German name with chlorine silver was known.
classification
Already in the outdated 8th edition of the mineral classification according to Strunz , the chlorargyrite belonged to the mineral class of the "halides" and there to the department of the "simple halides", where together with bromargyrite , carobbiite , halite , sylvite and villiaumite it belongs to the "halite series" the system no. III / A.02 .
In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. III / A.02-50 , which in the "Lapis system" also corresponds to the section "Simple halides". Here it forms together with Bromargyrit, Carobbiit, Griceit , Halit, Sylvin and Villiaumit a common but unnamed group.
In contrast , 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 chlorine argyrite in the more finely subdivided division of “simple halides without H 2 O”. This is also further subdivided according to the molar ratio of metal (M) to halogen (X), so that the mineral can be found in the sub-section “M: X = 1: 1 and 2: 3”, where it is only together with bromogyrite the "chlorogyrite group" with the system no. 3.AA.15 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns chlorine argyrite to the “halides” class and division of the same name. Here he is together with Embolite and Bromargyrite in the " Embolite Group " with the system no. 01/09/04 to be found in the subsection "Anhydrous and hydrous halides with the formula AX".
Chemism
The ideal theoretical composition of chlorine argyrite (AgCl) consists of 75.26% by weight of silver (Ag) and 24.74% by weight of chlorine (Cl).
Since chlorine argyrite forms a complete series of mixed crystals with bromine argyrite (AgBr), some of the chlorine is occasionally replaced ( substituted ) by bromine in natural chlorine argyrite samples . For example, bromine contents of up to 15.85% by weight were measured in samples from Broken Hill in Australia. In addition, small amounts of iodine (I) as well as mercury (Hg) and sodium (Na) were found in various samples .
Crystal structure
Chlorargyrite crystallizes isotypically with bromargyrite in the cubic crystal system in the space group Fm 3 m (space group no. 225) with the lattice parameter a = 5.55 Å and 4 formula units per unit cell .
The crystal structure of chlorogyrite corresponds to the sodium chloride structure ( halite structure ), only that the sodium ions in the unit cell are replaced by silver ions.
properties
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morphology
Chlorargyrite usually forms coarse, horn-like masses and crusty coatings. The waxy flowing masses known as buttermilk ore are also known . More rarely it is found in the form of stalactic or coral-like or fibrous aggregates.
Well-formed crystals are very rare and usually only a few millimeters in size. Common cubic shapes are cube {100}, octahedron {111} and rhombic dodecahedron {110} and their combinations. Twins after the octahedral surface (111) are also known.
Three Perfect Chlorargyrite Cubes
{100}
Cuboctahedron
combination of {100} and {111}
Combination of
{111}, {100} and {110}
With associated phyllosilicates Chlorargyrite can loose, blue and brown colored mixture form, in the mountain moist has a soft, semi-liquid consistency condition and therefore already in the miners' language of the 17th century as Buttermilcherz was called. The buttermilk ore , flowing from tunnels and drusen, was collected by the miners and reduced to fine silver in the hut fire. After a while in the air, however, it got tough on its own.
Chemical properties
Chlorargyrite is sensitive to light and, due to the formation of elemental silver, initially turns gray and its weathering product silver sulfide (Ag 2 S) finally turns brown to black.
In front of the soldering tube , chlorogyrite melts easily (approx. 450–500 ° C) while boiling to a gray, brown or black pearl and can easily be reduced to elemental silver . It is hardly attacked by acids, but it dissolves gradually in ammonia (NH 3 ). Under the action of potassium cyanide lye (KCN), a reddish-brown fog quickly forms on the chlorogyrite, which, when washed off, leaves a dark etched surface.
Modifications and varieties
The mixed crystals of the series Chlorargyrite – Bromargyrite are called embolite (Ag (Br, Cl)) and the mixed crystals of the series Chlorargyrite – Bromargyrite – Jodargyrite are called iodobromite (Ag (Br, Cl, I)) .
Education and Locations
Chlorargyrite forms as a secondary mineral in the oxidation zone of hydrothermal silver - deposits and under arid climate conditions in weathering deposits of the Red Bed type . As Begleitminerale shall be complementary to native silver, you still Akanthit , Atacamit , Cerussite , jarosite , Jodargyrit and Malachite on.
Chlorargyrite has already been proven to be a frequent mineral formation at many sites, with more than 1,600 sites being known to date (as of 2019). In addition to its type locality in Marienberg, the mineral appeared in many other places in Saxony, including the “Himmlisch Heer” mine near Cunersdorf (Annaberg-Buchholz) , in the Freiberg district , near Johanngeorgenstadt , Neustädtel (Schneeberg) and in the Schwarzenberg district . Furthermore, it was found in Germany in several places in the Black Forest (Baden-Württemberg), Odenwald (Hesse), near Sankt Andreasberg in the Harz (Lower Saxony), on the Königsberg in Rhineland-Palatinate,
The only secure site in Austria is the Stockerstollen on the Silberberg near Brixlegg - Rattenberg in Tyrol. Another find in the "Hocheck Mine" near Annaberg in Lower Austria has not yet been confirmed.
Other locations include Argentina, Australia, Bolivia, Chile, China, France, Greece, Honduras, Italy, Japan, Canada, Kazakhstan, Madagascar, Morocco, Mexico, Namibia, New Zealand, Norway, Portugal, Russia, Slovakia, Spain, South Africa, Tajikistan, Czech Republic, Hungary, Peru, the United Kingdom (Great Britain) and the United States of America (USA).
use
Chlorargyrite consists of up to 75.3% silver and was therefore an important silver ore when it was locally accumulated. Since the rich zones of silver-bearing deposits are usually mined, natural chloargyrite is rarely found today. A significant ore deposit for silver, lead and zinc is still the Broken Hill Mine in Australia, which reopened in 2018.
See also
literature
- Jacobus Gesnerus (K. Gesner): Argentum cornupellucido simile . In: De omni rerum fossilium genere, gemmis, lapidibus, metallis, et huiusmodi, libri aliquot, plerique nunc . 1st edition. Tiguri (Zurich) 1565, p. 62–62 ( rruff.info [PDF; 1,2 MB ; accessed on August 20, 2017]).
- FS Beudant: Keragyre . In: Traité Élémentaire de Minéralogie . tape 2 . Chez Verdière, Paris 1832, p. 501–501 ( rruff.info [PDF; 461 kB ; accessed on August 20, 2017]).
- August Breithaupt: Cerargyrites chlorus or horn silver . In: Complete Handbook of Mineralogy . tape 2 . Arnoldische Buchhandlung, Dresden, Leipzig 1841, p. 315-317 ( rruff.info [PDF; 733 kB ; accessed on August 20, 2017]).
- Albin Weisbach: Chlorargyrite . In: Synopsis Mineralogica. Systematic overview of the mineral kingdom . JG Englehardt'sche Buchhandlung, Freiberg 1875, p. 37–38 ( rruff.info [PDF; 404 kB ; accessed on August 20, 2017]).
- GT Prior, LJ Spencer: The cerargyrite group (holohedral-cubic silver haloids) . In: Mineralogical Magazine . tape 13 , 1902, pp. 174–185 ( rruff.info [PDF; 520 kB ; accessed on August 20, 2017]).
Web links
- Mineral Atlas: Chlorargyrite
- Chlorargyrite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on April 22, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Chlorargyrite. In: rruff.geo.arizona.edu. Accessed April 22, 2019 .
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 Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 319-320 .
- ↑ a b c d Chlorargyrite . 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; 61 kB ; accessed on November 28, 2018]).
- ↑ Chlorargyrite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 22, 2019 .
- ↑ a b c Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 240 .
- ↑ a b c d Thomas Witzke : The discovery of Chlorargyrit. In: strahlen.org/tw/. Retrieved April 22, 2019 .
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
- ^ A b David Barthelmy: Chlorargyrite Mineral Data. In: webmineral.com. Accessed April 22, 2019 .
- ^ A b Paul Ramdohr : The ore minerals and their adhesions . 4th, revised and expanded edition. Akademie-Verlag, Berlin 1975, p. 1174-1175 .
- ↑ Natural History Museum Berlin - Chlorargyrite ( Memento from March 4, 2016 in the Internet Archive )
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 193 .
- ↑ AG Betechtin (А. Г. Бетехтин): Textbook of special mineralogy . 2nd Edition. VEB Verlag Technik, Berlin 1957, p. 252–253 (as Kerargyrit) (Russian: Курс минералогии . Translated by Wolfgang Oestreich).
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 486 (first edition: 1891).
- ↑ Localities for Chlorargyrite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 22, 2019 .
- ↑ Find location list for Chlorargyrite at the Mineralienatlas and at Mindat
- ↑ 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 .
- ^ Sofie Wainwright, Declan Gooch: Jobs boost for mining sector in Broken Hill as government approves plan to reopen mine. In: abc.net.au. ABC News, January 2, 2018, accessed April 22, 2019 .