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Jarosite Crystals

The Mineral jarosite

Chemical Formula KFe3+3(SO4)2(OH)6
Composition Basic hydrous potassium iron sulfate
Color Yellow-brown, brown, orange-brown
Streak Light yellow
Hardness 2.5 - 3.5
Crystal System Hexagonal
Crystal Forms
and Aggregates
Occurs only in tiny crystals, which are hexagonal or triangular shaped, and may also be tabular or pseudocubic. Also occurs grainy, as fibrous crusts, in nodules, and in thin, hexagonal scales.
Transparency Translucent
Specific Gravity 2.9 - 3.3
Luster Resinous to adamantine
Cleavage 2,1 - basal (usually cannot be determined)
Fracture Conchoidal, uneven
Tenacity Brittle to slightly sectile
In Group Sulfates; Hydrous Sulfates
Striking Features Crystal habits and color
Environment Jarosite is a secondary mineral that forms through weathering in arid regions.
Rock Type Sedimentary, Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


Jarosite is not an industrially important mineral or of any interest to mineral collectors. However, it is popular among micromount collectors who find this mineral, which only occurs in small crystals, interesting in shape and color.

Jarosite is not a common mineral. It is found in the Jaroso Ravine in Sierra Almagrera, Spain, the locality for which it was named after. It is also found in Spain in the La Murta Mine, Castellon. Other localities are Caldbeck Fells, Cumbria, England; the Clara mine in Rankach, Baden-Wurttemberg, Germany; Huanani, Bolivia; and Sierra Pena Blanca, Chihuahua, Mexico.

In the U.S., it exists in several localities in Nevada, specifically at the Silver Coin Mine, Valmy, Humboldt Co.; Majuba Hill, Pershing Co.; and Esmeralda Co. Other occurrences are Bisbee and Tombstone, Cochise Co., Arizona; the Tintic District, Juab Co., Utah; the Iron Arrow Mine, Chaffee Co., Colorado; and Girard, Burke Co., Georgia.

Pyrite, Galena, Hematite, Barite, Variscite, Turquoise

Jarosite's crystal forms combined with its color easily identify it. However, poorly crystallized examples and massive forms of Jarosite may be difficult to distinguish from other minerals, such as Limonite. Jarosite is also indistinguishable from its isomorphous mineral Natrojarosite by ordinary methods.

jarosite PHOTOS
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