Piemontite
Ca2(Al2Mn3+)[Si2O7][SiO4]O(OH)IMA symbol: Pmtapproved
Piemontite is a silicate mineral with the formula Ca2(Al2Mn3+)[Si2O7][SiO4]O(OH), crystallizing in the monoclinic system. It has a Mohs hardness of 6.5, typically black, brown or red in color, with a pearly or vitreous luster, a specific gravity of 3.404. Its streak is red.
Photos
Crystallography
| Crystal system | monoclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | P 1 21/m 1 |
| Cell (Å, °) | a = 8.8727, b = 5.6686, c = 10.1682; α = 90, β = 115.48, γ = 90 |
| Cell volume | 461.675 ų, Z = 2 |
| Axial ratios | 1.5652:1:1.7938calculated from COD 9015882 |
| Source structure | COD 9015882 (American Mineralogist, 2010) — 1 of 22 structures |
Physical properties
| Density (calculated) | 3.433 g/cm³calculated from COD 9015882 |
|---|---|
| Hardness (Mohs) | 6.5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.404 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | black, brown, redsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | redsingle sourceWikidata (CC0) redsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | pearly, vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 9.BG.05Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.BG.05aWikidata (CC0) |
| Dana (8th) | 58.2.1a.11Wikidata (CC0) |