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Chemical Formula | CaMnSi2O6 |
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Composition | Calcium manganese silicate, sometimes with some iron |
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Variable Formula | Ca(Mn,Fe)Si2O6 |
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Color | Gray, brownish-gray, greenish-gray, cream |
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Streak | White |
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Hardness | 5 - 6 |
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Crystal Forms and Aggregates |
(Monoclinic) Occurs in elongated and stubby prismatic crystals, in thick tabular crystals, in radiating and fibrous aggregates, massive, and in rounded masses. |
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Transparency | Translucent to nearly opaque |
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Specific Gravity | 3.4 - 3.6 |
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Luster | Vitreous to greasy |
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Cleavage | 1,2 - prismatic at cleavage angles of 87º
and 93º (characteristic of minerals in the pyroxene group). May also exhibit parting in one direction. |
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Fracture | Uneven to splintery |
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Tenacity | Brittle |
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In Group | Silicates ; Inosilicates ; Pyroxene group |
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All About | Johannsenite is a rare member of the pyroxene group that is isomorphous with Diopside and Hedenbergite. It usually occurs with black manganese oxide dendrites on its surface. Johannsenite alters to become Rhodonite. |
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Striking Features | Crystal habits, localities, color, and cleavage habits |
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Popularity (1-4) | 3 |
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Prevalence (1-3) | 3 |
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Demand (1-3) | 3 |
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Distinguishing Similar Minerals |
The localities and crystal habits of this mineral can distinguish from almost all minerals. |
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Commonly Occurs With |
Rhodonite, Bustamite, Pyrolusite, Sphalerite, Quartz, Calcite, Wollastonite |
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Noteworthy Localities |
Johannsenite is found in Monte Civillina, Recoaro, Italy, and in Broken Hill, New South Wales, Australia. In the U.S. it occurs in Hanover, Grant County, New Mexico; the Iron Cap mine, Landsman Camp, Graham Co., Arizona; and Franklin, Sussex Co., New Jersey. |
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Picture Links | Sorry. No Images currently available. |
