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The Mineral rammelsbergite
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Rammelsbergite belongs to the Loellingite group, which is a group of chemically related isomorphous minerals that are all rare. Other members discussed in this guide are Loellingite and Safflorite. Rammelsbergite was named after the German scientist K.F. Rammelsberg (1812-1899). |
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Chemical Formula |
NiAs2 |
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Composition |
Nickel arsenide, sometimes with some cobalt and iron. If the nickel (Ni) is replaced by more than 50% iron (Fe), the mineral is not Rammelsbergite, but Loellingite, and if it is replaced by more than 50% cobalt (Co), the mineral is Safflorite. |
| Variable Formula |
(Ni,Fe,Co)As2 |
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Color |
Silver-white with a reddish tint. Tarnishes yellow or pink. |
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Streak |
Gray |
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Hardness |
5.5 - 6 |
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Crystal System |
Orthorhombic |
Crystal Forms
and Aggregates |
Seldom occurs in crystals, which are tabular and short prismatic. Most commonly occurs massive, but also grainy, fibrous, and in coxcomb aggregates. |
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Transparency |
Opaque |
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Specific Gravity |
6.9 - 7.1 |
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Luster |
Metallic |
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Cleavage |
None |
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Fracture |
Uneven |
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Tenacity |
Brittle |
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In Group |
Sulfides; Arsenides |
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Striking Features |
Color and tarnish, crystal habits |
| Environment |
In medium temperature cobalt and nickel veins. |
| Rock Type |
Sedimentary, Metamorphic |
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Popularity (1-4)
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4 |
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Prevalence (1-3)
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3 |
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Demand (1-3) |
3 |
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Rammelsbergite is a rare mineral, and its localities are limited. Occurrences include Kongsberg, Norway; Ste Marie-aux-Mines, Alsace, France; Schneeberg, Saxony, Germany; Binntal, Switzerland; and Aït Ahmane, Bou Azzer, Morocco.
Rammelsberg was found in Mexico in the Silver mines of Batopilas, Chihuahua. In Canada it occurs in the Eldorado mine near the Great Bear Lake, Northwestern Territories, and in Cobalt, Timiskaming District, Ontario. In the U.S., Rammelsbergite was found in the Mohawk mine, Keweenaw Co., Michigan; and in the Trotter Dump, Franklin, Sussex Co., New Jersey.
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Arsenopyrite - Difficult to distinguish, but contains sulfur attributes which are lacking in Rammelsbergite.
Skutterudite, Loellingite, and Safflorite - Indistinguishable without x-ray analysis.
Pyrite, Marcasite, and Pyrhottite - Occur in different crystals, more yellow in color.
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