Acanthite is an unusual mineral that contains silver sulfide.
Origin of the name: The name of acanthite comes from the Greek word "acanthus" - spike (due to the characteristic shape of the crystals)
Varieties of the mineral:
Acanthite is stable at temperatures below 179 degrees Celsius. Silver sulfide of cubic modification, stable at temperatures above 179 degrees Celsius - argentite. In air, argentite is replaced by acanthite.
The properties
Syngonia: Monoclinic
Composition (formula): Ag2S
Colour:
Lead grey to black
Dash colour (powder colour): Dark Lead Gray
Transparency: Opaque
Cleavage: Imperfect
Kink: Rough
Gloss: Metallic
Hardness: 2-2.5
Specific gravity, g / cm3: 7.2-7.4
Special Features:
In nitric acid it dissolves with the release of sulfur; when hydrochloric acid is added, a curdled white precipitate of AgCl is formed, soluble in ammonia. At high temperatures, acanthite becomes a conductor of electricity.
Selection form
Own acanthite crystals formed at temperatures below 179 degrees Celsius have a columnar, spear-like appearance. More often there are pseudomorphs of acanthite on argentite in the form of cubic, cuboctahedral, occasionally rhododecahedral crystals, also in the form of polysynthetic twins. Acanthite is often found in silver nigra, a black, powdery coating that consists of a mixture of silver minerals.
The main diagnostic signs
Macroscopically acanthite is difficult to determine.
Appearance What does it look like? Acanthite is an opaque stone of a dark gray or black shade with a characteristic lustre for silver. Shades may vary slightly and reach lead. Its edges are very sharp and resemble spikes. With prolonged exposure to light, the stone darkens. They frame it with a needle and a knife.
Associated Minerals
Native silver, proustite, pyrargyrite and other silver sulfosalts, cerussite, chlorargyrite
Origin
Acanthite is found in hydrothermal silver and silver-containing sulfide deposits. However, most often acanthite is observed in the lower parts of the oxidation zones of these deposits in association with native silver, chalcone, and chlorargyrite.
Deposits / Manifestations
Russian deposits: Mangazeyskoye, Forecast, Khachakchan, Night (East Yakutia); Dukat, Juliet, Lunnoye, Karamken (Magadan region); Khakanja (Khabarovsk Territory); Asgat, Grekhovskoe, Zmeinogorskoe (Altai) and others.
Foreign deposits: Guanohuato, Batopilas, Chihuahua, Durango and other numerous deposits of Chile and Mexico; Portobelo Mine (Ecuador); Kongsberg (Norway); Freiberg, Annaberg (Germany); Banska Štiavnica (Slovakia) and others.
Application
Acanthite as a satellite of other silver-containing minerals is part of silver ores and is a source of silver.
Historical data
The first mention was in antiquity, namely in the 16th century. The famous scientist Agricole touched on this topic in his writings. In more detail, natural stone was studied only in the 19th century. Scientists have learned that 87 per cent of the stone is silver. Outwardly, it is compared with galena.
Mine Where is it mined? The Acanthite deposit is the Czech Republic. It is there that crystals can be found most likely. There are practically no large deposits of stone or they are little known. Pseudomorphs of a rather large size (up to 7 cm) are found in Mexico. Also, deposits can be found in other countries - these are Germany, the USA, Norway and Canada. Acanthite is found in Russia only in the Urals and East Transbaikalia.
Magical properties The stone has unusual properties and can positively affect intuition, as well as protect from bad looks and the evil eye. It is especially suitable for creative people.
Acanthite - silver sulfide. The term "argentite" is formally used for its high-temperature modification, but in fact these names are synonyms. Composition - Ag2S. The silver content is more than 87%. In nature, this substance occurs in the form of two different modifications: acanthite is formed at temperatures up to 179 ° C.
It occurs in the form of continuous dense masses, inclusions, deposits, crystalline dendrites.