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Formula: AgCl
Chloride of silver,
chlorargyrite group
Crystal System: Isometric
Specific gravity: 5.5 to 5.6 measured, 5.57 calculated
Hardness: 1½
Streak: White to grey
Colour: Colourless, white, yellowish, brownish, grey, black
Melts at 455°
Common impurities: I
Environments:
Chlorargyrite is a secondary mineral found in the
oxidation zone of
silver deposits, especially in arid regions, and in
epithermal (low temperature) veins. It is
found associated with native silver,
cerussite and other
secondary minerals.
Localities
At the Broken Hill district, Yancowinna county, New South Wales, Australia, the deposit originally formed in a shallow
lake or submarine rift and now comprises an intensely
granulite and upper
amphibolite facies metamorphosed and deformed
sequence of sedimentary and volcanic rocks, and minor iron-rich and
Chlorargyrite occurs in vuggy coronadite with
goethite,
sometimes associated with smithsonite. It is also found with
cerussite, dolomite and
malachite. At deeper levels it is a late-stage mineral in the
arsenate zones,
associated with carminite and members of the
segnitite to beudantite series
(AJM 3.1.34).
Chlorargyrite from Broken Hill - Image
At Johanngeorgenstadt, Erzgebirgskreis, Saxony, Germany, in the 17th and 18th centuries, large amounts of
chlorargyrite were found in the upper parts of the ore veins. It occurred as waxy white to glittery brown,
green, bluish, grey and almost black masses, as bud-like to fibrous, hairlike forms, and in sharp, cubic crystals.
Among the associated minerals were limonite and a little
palygorskite. Chlorargyrite was also commonly found intergrown
with cerussite, as at the Neujahr Maassen mine.
In the final period of mining—from 1945 to 1958—during which only uranium
ores were produced, isolated unworked ore veins were discovered, and chlorargyrite was found in their
oxidation zones.
There remains to be mentioned a strange fluid-like to gelatinous type of chlorargyrite referred to by miners
as buttermilk ore or moon milk. It is a mixture of chlorargyrite and other minerals that takes a viscously
fluid form. Chlorargyrite was mined in fair quantities from the upper portions of ore veins, having been
deposited there predominantly by precipitation of silver chloride from solutions. Initially it formed viscous
suspensions which thickened gradually to paste-like deposits and finally to more or less solid bodies. Today,
“buttermilk ore” is among the greatest rarities
(MinRec 55.5.593-595).
Chlorargyrite from Johanngeorgenstadt -
Image
The type locality is the Marienberg mining district, Erzgebirgskreis, Saxony, Germany.
At the San Rafael Mine, Quartz Mountain camp, Lodi Mining District, Lodi Hills, Nye County, Nevada, USA,
chlorargyrite and bromargyrite occur sparingly, associated with
mimetite, anglesite and
bayldonite
(R&M 85.6.516).
Chlorargyrite from the San Rafael Mine -
Image
At the Tintic Mining District, Juab County, Utah, USA, probably the most common
silver mineral of the District, chlorargyrite, has been found in many
of the mines, particularly where galena and other
lead minerals are more common. At the Trixie mine in the East Tintic
chlorargyrite occurs directly with hessite,
native silver and native gold. It is
most commonly found as brown smears that look like dirt; however, crystallized chlorargyrite has also been
found at the Trixie mine.
At the nearby Tintic Standard mine, chlorargyrite rich in bromine has also been found, as solid masses up to
5 cm in size
(MinRec 55.2.190-192).
Chlorargyrite from the Tintic Mining District -
Image
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