Alstonite
BaCa(CO3)2IMA symbol: Asngrandfathered
Alstonite is a carbonate or nitrate mineral with the formula BaCa(CO3)2, crystallizing in the triclinic system. It has a Mohs hardness of 4-4.5, typically colorless, white, gray or pink in color, with a vitreous luster, a specific gravity of 3.718. Its streak is white.
Photos
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Crystallography
| Crystal system | triclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | P 3 1 m |
| Cell (Å, °) | a = 17.436, b = 17.436, c = 6.1295; α = 90, β = 90, γ = 120 |
| Cell volume | 1613.8 ų, Z = 12 |
| Axial ratios | 1.0000:1:0.3515calculated from COD 9017723 |
| Source structure | COD 9017723 (Mineralogical Magazine, 2020) |
Powder X-ray diffraction (calculated)
| d (Å) | 3.552 | 2.507 | 2.054 | 1.945 | 2.517 | 1.85 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 31.5 | 31.5 | 25.5 | 23.9 | 19.4 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9017723; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.672 g/cm³calculated from COD 9017723 |
|---|---|
| Hardness (Mohs) | 4-4.5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.718 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | colorless, gray, pink, whitesingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | whitesingle sourceWikidata (CC0) |
| Luster | vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 297.42 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Ba 46.17%, Ca 13.48%, C 8.08%, O 32.28% |
Classification
| Nickel-Strunz (10th) | 5.AB.35Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 5.AB.35Wikidata (CC0) |