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Jarosite Crystals

The Mineral jarosite

Jarosite is both an individual mineral, as well a group name of several similar minerals. Jarosite is the most common member of the group; some of the other rare members include Ammoniojarosite, Argentojarosite, Beaverite, Dorallcharite, Hydroniumjarosite, Natrojarosite, and Plumbojarosite.

Jarosite was first described in 1852 by German mineralogist August Breithaupt in type locality of Barranco Jaroso in the Sierra Almagrera in Southern Spain. In 2004, it was detected by the exploration rover Opportunity on Mars, indicating the possible presence of water that once existed on Mars.
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
Generally only is small crystals, which are hexagonal or triangular shaped, and may also be tabular or pseudocubic. Also drusy, 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 Forms through weathering in arid regions as a secondary mineral.
Rock Type Sedimentary, Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


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

Jarosite is not a common mineral. It has been found in the Jaroso Ravine in Sierra Almagrera, Spain, the type locality for which it was named after. It is also found in Spain in the La Murta Mine, Castellon. Other European localities for Jarosite 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., Jarosite exists in several localities in Nevada, specifically at the Silver Coin Mine, Valmy, Humboldt Co.; Majuba Hill, Pershing Co.; and the Gilbert District, Goldfield, 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. An important Mexican locality for Jarosite is Sierra Peña Blanca, Chihuahua.

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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