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Chemical Formula | KFe3+3(SO4)2(OH)6 |
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Composition | Basic hydrous potassium iron sulfate |
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Color | Yellow-brown, brown, orange-brown |
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Streak | Light yellow |
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Hardness | 2½ - 3½ |
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Crystal Forms and Aggregates |
(Hexagonal) 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. |
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Transparency | Translucent |
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Specific Gravity | 2.9 - 3.3 |
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Luster | Resinous to subadamantine |
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Cleavage | 2,1 - basal (usually cannot be determined) |
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Fracture | Conchoidal, uneven |
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Tenacity | Brittle to slightly sectile |
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Other Names |  Utahite |
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In Group | Sulfates ; Hydrous sulfates |
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Uses | Jarosite is not an industrially important mineral or of any interest to mineral collectors. It is, though, very popular among micromount collectors who find this mineral, which only occurs in tiny examples, interesting in shape and color. |
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Striking Features | Crystal habits and color |
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Popularity (1-4) | 3 |
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Prevalence (1-3) | 3 |
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Demand (1-3) | 2 |
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Distinguishing Similar Minerals |
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. |
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Commonly Occurs With |
Variscite, Pyrite, Galena, Hematite, Barite, Turquoise |
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Noteworthy Localities |
Jarosite is a secondary mineral that forms through weathering in arid regions, and is uncommon. It is
found in the Jaroso Ravine in Sierra Almagrera, Spain,
for which it was named after. It also occurs in Caldbeck
Fells, Cumbria, England; the Clara mine in the Black
Forest of Germany; Burra Burra, South Australia; the Los
Bayos mine, Sierra Gordo, Chile; and Huanani, Bolivia. In the U.S., lustrous crystals associated with Hematite were found in the Iron Arrow Mine in Chaffee Co., Colorado. It was also found as thin hexagonal scales in the Shattuck-Arizona Mine in Bisbee, Cochise Co., Arizona. Other localities are the Vulture Mine, Maricopa Co., Arizona; the Tintic District, Juab Co., Utah; Cherry Creek, Mackay district, Custer Co., Idaho; and the Champion mine in Mono Co., California. |
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