Carbonates: Ankerite
Diagnostic Card.
In the photo: a single crystal ankerite in the host rock. Bottom: dark colored crystals from Val Chisone (Turin Province).
Ca Fe (CO 3)2
Crystal system trigonal
Hardness of 3.5-4
Specific Gravity 2.97
Cleavage is perfect
fracture polurakovisty
Colour colorless, differently colored
Color white powder
Shine from glass to pearl
It crystallizes in the trigonal rhombohedral crystals singonii.Dovolno common appearance, for the most part combined into aggregates. Most forms of mass ankerite enough solid build. It has a perfect cleavage parallel to the faces of the rhombohedron. Color changes from white to gray, tan, brown, depending on the amount of iron in the composition of the mineral. Ankerite fragile, translucent, has a sheen of glass to pearl. In the air it oxidizes quickly, getting darker as a result.
Chemical composition. The double salt (see. Also dolomite). Poor iron kind called brown spar. Ankerite constantly contains magnesium and manganese. The ratio of iron and manganese varies widely. Transparency. Opaque, translucent. Form crystals. rhombohedron; Crystals often curved faces like dolomite. The crystal structure. Lattice calcite. Class symmetry. Rhombohedral - 3. Cleavage. According rhombohedron (1010). Aggregates. The solid, grainy.
Diagnostic features.
Soluble in cold hydrochloric acid. The oxidation becomes brown and cracks. Behavior in acids. It behaves as dolomite; released only by heating to form CO2 bubbles.
Origin.
It often occurs as one of the minerals that performs vein ore deposits! masses. It may also be present as an accessory mineral in some igneous rocks (diorites, quartz porphyries).
Deposits and application.
In Italy ankerite present in geodes porphyry Guasso al Monte (Province of Varese), in quartz veins Carona (Bergamo province), in a lead mine in Monteneve (Bolzano province). Detected as in France, Hungary, the United States, Colombia, Namibia and Algeria. Being a common mineral, ankerite is not used in the mining industry, because it does not form large clusters and, in addition, contains much iron is insufficient. Therefore, it is regarded as a mineral having an extremely scientific and collector value.
Quartz crystals overgrown ankerite. Odud, Pamir, Tajikistan. Photo: © AA Evseev.
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