| Alstonite | |
|---|---|
 | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | BaCa(CO3)2 |
| IMA symbol | Asn[1] |
| Strunz classification | 5.AB.35 |
| Dana classification | 14.02.05.01 |
| Crystal system | Triclinic Unknown space group |
| Unit cell | a = 17.38, b = 14.40 c = 6.123 [Å]; α = 90.35° β = 90.12°, γ = 120.08°; Z = 24[2] |
| Identification | |
| Formula mass | 297.42 g/mol[3] |
| Colour | Colourless to snow-white; also pale gray, pale cream, pink to pale rose-red |
| Crystal habit | Steep pseudohexagonal dipyramids, pseudo-orthorhombic |
| Twinning | Common on pseudo-orthorhombic {110} and {310}[4] |
| Cleavage | Imperfect on pseudo-orthorhombic {110}[4] |
| Fracture | Uneven |
| Mohs scale hardness | 4 to 4.5 |
| Lustre | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.70 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.526 nβ = 1.671 nγ = 1.672 |
| Birefringence | δ = 0.146 |
| Pleochroism | None |
| 2V angle | Measured 6°, calculated 8° |
| Dispersion | Weak, r > v |
| Ultraviolet fluorescence | Weak yellow under LW and SW |
| Solubility | Soluble in dilute HCl |
| Alters to | Colour may fade on exposure to light |
| Other characteristics | Not radioactive |
| References | [3][2][5][6] |
Alstonite, also known as bromlite,[6] is a low temperature hydrothermal mineral[6] that is a rare double carbonate of calcium and barium with the formula BaCa(CO
3)
2, sometimes with some strontium.[5] Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous. Alstonite is triclinic but barytocalcite is monoclinic and paralstonite is trigonal. The species was named Bromlite by Thomas Thomson in 1837 after the Bromley-Hill mine,[7] and alstonite by August Breithaupt of the Freiberg Mining Academy in 1841, after Alston, Cumbria, the base of operations of the mineral dealer from whom the first samples were obtained by Thomson in 1834. Both of these names have been in common use.[8]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b Mineralienatlas
- ^ a b Webmineral data
- ^ a b Cite error: The named reference
HOMwas invoked but never defined (see the help page). - ^ a b Gaines et al. (1997) Dana’s New Mineralogy, Eighth Edition. Wiley
- ^ a b c Mindat.org
- ^ Thomas Thomson, This mine was owned by Thomas Shaw and business partner Jacob Walton between 1816 and 1874, The owners then Subcontracted to groups of independent miner, basing their pay on the amount of drifting accomplished, the amount of ore produced, or a combination of the two, . This system worked well, and the Brownley Hill mine became one of the more productive mines on Alston Moor during the Middle 1800s. by the early 1870s the seems of lead were being exhausted and in 1874 the lease was then taken over by the Brownley Hill Mining which concentrated on Zinc mining, which failed to make a profit. "On the Right Rhombic Baryto-Calcite, with reference to Prof. Johnston’s Paper in the Phil. Mag. for May 1837", The London and Edinburgh Philosophical Magazine and Journal of Science, vol. XI, july-december 1837, p. 48
- ^ Cite error: The named reference
EB1911was invoked but never defined (see the help page).