Chlorargyrite
- Silver chloride
- Horn silver, Hornerz, Silberhornerz
- Cerargyrit, Kerargyrit
Chlorargyrite is a commonly occurring mineral from the mineral class of " halides ". It crystallizes in the cubic crystal system with the chemical composition AgCl, is so chemically seen a silver chloride ( also silver chloride ).
Chlorargyrite found mostly in the form of massive aggregates or crusty coatings, but also develops small cubic crystals and combinations, and twins after the octahedral surface. In pure form, the mineral is colorless and transparent, but by foreign admixtures, it often takes a light yellow to grayish-yellow color with a purplish hue, brownish or brownish green on, the transparency decreases accordingly. In the fresh state Chlorargyrite has a fat - to diamond-like luster, but will gradually dull due to weathering.
With a Mohs hardness of 1.5 to 2 Chlorargyrite heard similar to the reference minerals Talk ( 1) and gypsum ( 2) to the soft minerals that can be scratched with a fingernail.
Special Features
Chlorargyrite is light sensitive and discolored at first gray and its weathering product of silver sulfide ( Ag 2 S ) finally brown to black. Due to the formation of elemental silver
Before the blowpipe Chlorargyrite light ( 450-500 ° C ) melts easily be reduced to a gray, brown or black pearl and can lead to elemental silver under boil. From acids it is as good as not attacked in ammonia it dissolves, however gradually.
With associated phyllosilicates Chlorargyrite may form loose, blue - gray to brown -colored mixture, the mountain in the wet state has a soft, semi-liquid consistency and has therefore been referred to in the miners' language of the 17th century as Buttermilcherz. The Buttermilcherz was fluent of corridors and Druze, caught by the miners, reduced cabin fire to fine silver. After some time on the air, it was hard but also on its own.
Etymology and history
Chlorargyrite was known already in the 16th century as horn silver, Silberhornerz or short Hornerz because it resembled most fettgetränktem and transparent gewordenem so horn. A first mention, without further description can be found in the works of Georgius Agricola in 1530 ( Bermannus, sive de re metallica ), and his major work, 1546 ( De Natura Fossilium ) where the mineral the silver ores called Argentum rude purpureum or Argentum rude jecoris coloris (liver- colored silver ore ) is assigned.
A more detailed description of the mineral is narrated only by Johannes Mathesius and his mountain sermons that he wrote 1552-1562:
" " Auffm Marienberg is horn- colored silver broken / which is transparent / and schmiltzt VBER eim to Liechtenstein. In Fewer but wirdt einerley Weyss silver drauss / on the output of a geschmeydiger silver wirdt / because from the other. " "
As well as
" " Glaßertz but dignified VND Weyss silver / and what you zeyt newlicher auff Marienberg gehawen / is by carefully like a horn in a Lantern / and schmiltzt vberm Liecht / are what give it as long as " "
Refer here to a transparent, horn colored silver ore from Marienberg in the Erzgebirge, which can be assigned to the properties after Chlorargyrite.
A more clear description of the Chlorargyrits deliver 1565 John Kent Mann and Georg Fabricius, summarized in a textbook by Conrad Gesner and Georg Fabricius, which is the mineral also called " transparent horn farbs solid silver" ( Argentum, flavi coloris ) or " Läberfarben ertz " ( Argentum rewrite iecoris colore ) of Marienberg in the Erzgebirge. Therefore, this location is also considered the type locality.
In later sources Chlorargyrite so as Hornerz ( Werner, 1789), horn silver ( Hausmann, 1813) and Silberhornerz place under various synonyms, ( Leonhard, 1821) as well as meanwhile Greek derivations κέρας [ keras ] for Horn and ἄργυρος [ argyros ] for silver as Kérargyre ( Beudant, 1832), keratitis ( Haidinger, 1845), and Kerargyrite Cerargyrite ( Dana, 1855 and 1868 ).
The still valid Identification of Minerals as Chlorargyrite based on its composition, the chlorine on the one hand and the Greek word for silver ( argyros ) on the other hand, it finally received in 1875 by Albin Weisbach, wherein, by Carl Friedrich Naumann 1828 chloride of silver, even a purely German designation was known.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of Chlorargyrite to the mineral class of " halides " and then " Simple halides " to the Department of where he along with Bromargyrit, Carobbiit, Griceit, halite, sylvite and Villiaumit the " halite series" with the system number. III/A.02 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz 's Mineral classification assigns the Chlorargyrite also in the class of " halides ", there, however, in the already fine divided department of a "Simple halides, without H2O" one. This is also further subdivided by the molar ratio of metal ( M) halogen (X), so that the mineral according to its composition in the subsection "M: X = 1: 3: 1 and 2" is to find where it only together with the Bromargyrit " Chlorargyritgruppe " with the system number. 3.AA.15 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the Chlorargyrite in the class and division of the same name " halides ". Here he is with Embolit and Bromargyrit in the " Embolitgruppe " with the system no. 09:01:04 to find " water clear and hydrated halides with the formula AX" within the subdivision of.
Modifications and varieties
As Embolit (Ag (Br, Cl )), the mixed crystal series Chlorargyrite - Bromargyrit and as Jodobromit (Ag (Br, Cl, I) ) are referred to the mixed crystals of the series - Chlorargyrite Bromargyrit - Jodargyrit.
Education and Locations
Chlorargyrite forms as a secondary mineral in the oxidation zone of hydrothermal silver deposits and under arid climatic conditions in weathering deposits of the Red Bed type. Accompanying minerals occur in addition to native silver, you still acanthite, Atacamit, Cerussite, jarosite, Jodargyrit and malachite.
As a frequent mineral formation Chlorargyrite has already been demonstrated in many localities, where so far (as of 2012) are considered to be known around 1,400 localities. Apart from its type locality Marienberg the mineral still occurred in many other places in Saxony, so among other things, in the pit " heavenly army " at Cunersdorf ( Annaberg- Buchholz), in the district of Freiberg, Johann George Town, Neustädtel (Snow Mountain ) and in the district of Schwarzenberg. Furthermore, there was found in Germany in several places in the Black Forest (Baden- Württemberg), Odenwald (Hessen), at St. Andreas mountain in the Harz ( Lower Saxony), at Königsberg in Rhineland -Palatinate,
The only certain locality in Austria is the Stocker tunnel at Silver Mountain near Brixlegg rats in Tyrol. Another find in the " Hocheck Mine" at Annaberg in Lower Austria has not yet been confirmed.
Other localities lie among others in Argentina, Australia, Bolivia, Chile, China, France, Greece, Honduras, Italy, Japan, Kazakhstan, Madagascar, Mexico, Morocco, Namibia, New Zealand, Norway, Portugal, Russia, Slovakia, Spain, South Africa, Tajikistan, the Czech Republic, Hungary, Peru, the United Kingdom ( UK ) and the United States of America (USA).
Morphology
Chlorargyrite usually forms massive, horn- like masses and crusty coatings. Also known are those referred to as Buttermilcherz, waxy mass flow. Less frequently it is found in the form stalaktitischer or coral -like or fibrous aggregates.
Well -formed crystals are rare and usually only a few millimeters in size. Frequent cubic shapes are cube { 100}, {111 } octahedron and rhombic dodecahedron { 110} and combinations thereof. Even twins after the octahedral face (111 ) are known.
Cuboctahedron (combination of {100 } and { 111 })
Combination of {111 }, { 100} and { 110}
Crystal structure
Chlorargyrite crystallizes isotypic ( halite structure type ) with Bromargyrit in the cubic crystal system in the space group Fm3m ( Raumgruppen-Nr. 225 ) with the lattice parameters a = 5.55 Å and four formula units per unit cell.
Use
Chlorargyrite consists of up to 75.3 % silver and is therefore an important silver ore.