Thaumasite
Ca3Si(OH)6(CO3)(SO4)·12H2OIMA symbol: Tmagrandfathered
Thaumasite is a sulfate mineral with the formula Ca3Si(OH)6(CO3)(SO4)·12H2O, crystallizing in the hexagonal system. It has a Mohs hardness of 3-5, typically white in color, with a dull or greasy luster, a specific gravity of 1.877. Its streak is white.
Photos
Crystallography
| Crystal system | hexagonal crystal systemWikidata (CC0) |
|---|---|
| Space group | P 63 |
| Cell (Å, °) | a = 11.036, b = 11.036, c = 10.3845; α = 90, β = 90, γ = 120 |
| Cell volume | 1095.32 ų, Z = 2 |
| Axial ratios | 1.0000:1:0.9410calculated from COD 9014390 |
| Source structure | COD 9014390 (American Mineralogist, 2012) — 1 of 7 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 9.557 | 3.781 | 5.518 | 2.499 | 2.715 | 2.158 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 39.7 | 31.2 | 30.4 | 28.2 | 28 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9014390; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 1.888 g/cm³calculated from COD 9014390 |
|---|---|
| Hardness (Mohs) | 3-5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 1.877 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | whitesingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | whitesingle sourceWikidata (CC0) |
| Luster | dull, greasysingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 622.62 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Ca 19.31%, Si 4.51%, O 64.24%, H 4.86%, C 1.93%, S 5.15% |
Classification
| Nickel-Strunz (10th) | 7.DG.15Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 7.DG.15Wikidata (CC0) |
| Dana (8th) | 32.4.4.4Wikidata (CC0) |