Breunnerite
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| Breunnerite | |
|---|---|
 Breunnerite from Bolzano. Italy | |
| General | |
| Category | Carbonate mineral |
| Formula | (Mg, Fe) CO 3 |
| Crystal system | Trigonal[1] |
| Identification | |
| Color | from yellowish or gray-brown to brown |
| Cleavage | perfect on a rhombohedron |
| Mohs scale hardness | 4.0-4.5 |
| Luster | metallic |
| Diaphaneity | translucent to opaque |
| Density | 3.0-3.2 (calculated) |
Breunnerite, also known as brown spar[2]: 258 (German: braunspat) is a variety of magnesite, with a magnesium/iron ratio of 90/10 to 70/30.[1]
It has been described by Wilhelm Karl Ritter von Haidinger in samples of Pfitsch pass, Zamsergrund and Großer Mt Greiner, Zemmgrund, two cities of the Ziller Valley, Tyrol, Austria.[3]
Haidinger named the new variety of the magnesite in honor of Count August Breunner[4] (sometimes the family name is written as Breuner; 1796-1877), a famous collector of minerals and fossils, as well as a high-ranking government official of Austria-Hungary.[1]
In 19th-century mineralogy, as well as in mining and among geologists, breunnerite and its close analogues from the isomorphic series magnesite → siderite were more often known under the capacious morphological name ″brown spar″.[5]: 34
