Class: Carbonates (Nitrates)
Group: Calcite
A primary mineral in hydrothermal veins; in metamorphic deposits; common in
carbonatites; authigenic and secondary in sediments; uncommon in granite
pegmatites (
Anthony et al., 2001—2005). Faceted specimens are rare. The largest faceted specimen is a 59.65 carat from South Africa (
Arem, 1987: 162).
Original description: ‘Rhodochrosit’ Hausmann, J. F. L., 1813. Rhodochrosit — Handbuch der Mineralogie, Göttingen 3: 1081—1082 [
view in ‘Library’].
Type locality: Cavnic mine, Cavnic, Maramureș, Romania.
Type material: unknown.
Etymology: derived from the Greek words
ρόδο (rhodo) ‘rose’ and
χρώς (chros) ‘colouring’, referring to its colour.
Distribution: numerous localities; only a few for good specimens: Canada: Quebec, Mont Saint-Hilaire; China: Guangxi Zhuang, Wuzhou, Cangwu, Liubao, Wutong mine; Mexico: Chihuahua, Santa Eulalia; Sonora, Cananea; Peru: Lima, Cajatambo Province, Uchucchacua; South Africa: Cape Province, near Kuruman, Hotazel mine; USA: Colorado, Park Co., Alma, Sweet Home mine (
Anthony et al., 2001—2005).
Chemistry
Mn2+CO3
Essential elements: carbon (C), oxygen (O), manganese (Mn).
Crystal data
Crystallography: trigonal — hexagonal scalenohedral.
Crystal habit: crystals are rhombohedra {1011} or scalenohedra {2131}, to 12 cm, modified by {0001}, {1010}, {1120}, with several other forms, may be rounded or saddle-shaped; commonly in bladed aggregates, columnar, botryoidal, compact granular, massive.
Twinning: on {1012}, contact and lamellar, then flattened (
Anthony et al., 2001—2005).
Optical properties
Colour: pink, rose-red, cherry-red, yellow, yellowish grey, cinnamon-brown, may be banded; colourless in transmitted light (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent (
Anthony et al., 2001—2005).
Lustre: vitreous; pearly in aggregates (
Anthony et al., 2001—2005).
Refractive index: 1.578—1.82 — anisotropic [uniaxial (-)] (
Lazzarelli, 2012).
Birefringence: 0.208—0.22.
Dispersion: 0.015 (low).
Pleochroism: faint (
Arem, 1987: 162).
Material from ‘Repository’
1 specimen: 0028 — 0.50 ct, China, Guangxi Zhuang, Wuzhou, Cangwu, Wutong mine, 23.81°N 111.378°E.
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