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The Mineral rammelsbergite

Classic Old Rammelsbergite

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).

Chemical Formula

NiAs2

Color

Silver-white with a reddish tint. Tarnishes yellow or pink.

Crystal System

Orthorhombic

Properties

Streak
Gray
Hardness
5.5 - 6
Transparency
Opaque
Specific Gravity
6.9 - 7.1
Luster
Metallic
Cleavage
None
Fracture
Uneven
Tenacity
Brittle

Crystal Habits

Seldom occurs in crystals, which are tabular and short prismatic. Most commonly occurs massive, but also grainy, fibrous, and in coxcomb aggregates.

Additional Information

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.
In Group
Sulfides; Arsenides
Striking Features
Color and tarnish, crystal habits
Environment
In medium temperature cobalt and nickel veins.
Rock Type
Sedimentary, Metamorphic

Noteworthy Localities

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.

Common Mineral Associations

Loellingite, Chloanthite, Silver

Distingushing Similar Minerals

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.

rammelsbergite Photos



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