Barytocalcite
Barytocalcite is an anhydrous barium calcium carbonate mineral with the chemical formula BaCa(CO3)2. It is trimorphous with alstonite and paralstonite, that is to say the three minerals have the same formula but different structures. Baryte and quartz pseudomorphs after barytocalcite have been observed.
| Barytocalcite | |
|---|---|
Barytocalcite from England | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | BaCa(CO3)2 |
| IMA symbol | Bcal |
| Strunz classification | 5.AB.45 |
| Dana classification | 14.02.06.01 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/m |
| Unit cell | a = 8.1 Å, b = 5.2 Å, c = 6.5 Å, β = 106°; Z = 2 |
| Identification | |
| Formula mass | 297.42 g/mol |
| Colour | Colourless, white, greyish, greenish, yellowish |
| Crystal habit | Prismatic, drusy, massive – granular |
| Cleavage | Perfect in at least two directions |
| Tenacity | Brittle |
| Mohs scale hardness | 4 |
| Luster | Vitreous to resinous |
| Streak | White |
| Diaphaneity | Translucent to transparent |
| Specific gravity | 3.64 to 3.71 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.525, nβ = 1.684, nγ = 1.686 |
| Birefringence | δ = 0.161 |
| 2V angle | Measured: 15°, calculated: 10° |
| Dispersion | Relatively weak, r>v |
| Ultraviolet fluorescence | Fluorescent dull yellow under LW and SW UV |
| Solubility | Soluble in dilute HCl |
| References | |
Barytocalcite crystallizes in the monoclinic crystal system, typically as massive to druzy accumulations of transparent white to yellow to grey aggregates of slender prismatic crystals. It has a Mohs hardness of 4 and a specific gravity of 3.64 to 3.71.
It was first described in 1824 for an occurrence in the Blagill Mine in North Pennines, Cumbria (Cumberland), England, and named for its composition.
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