Pyrophyllite
Al2Si4O10(OH)2IMA symbol: Prlgrandfathered
Pyrophyllite is a silicate mineral with the formula Al2Si4O10(OH)2, crystallizing in the triclinic system. It has a Mohs hardness of 1-2, typically white, brown, gray or green in color, with a dull or pearly luster, a specific gravity of 2.8-2.9. Its streak is white.
Photos
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Crystallography
| Crystal system | triclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | C -1 |
| Cell (Å, °) | a = 5.16, b = 8.966, c = 9.347; α = 91.18, β = 100.46, γ = 89.64 |
| Cell volume | 425.157 ų, Z = 4 |
| Axial ratios | 0.5755:1:1.0425calculated from COD 9000809 |
| Source structure | COD 9000809 (American Mineralogist, 1981) — 1 of 3 structures |
Physical properties
| Density (calculated) | 2.799 g/cm³calculated from COD 9000809 |
|---|---|
| Hardness (Mohs) | 1-2single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 2.8-2.9 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | brown, gray, green, white, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | whitesingle sourceWikidata (CC0) |
| Luster | dull, pearlysingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 360.31 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Al 14.98%, Si 31.18%, O 53.28%, H 0.56% |
Classification
| Nickel-Strunz (10th) | 9.EC.10Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.EC.10Wikidata (CC0) |
| Dana (8th) | 71.2.1.1Wikidata (CC0) |