Andalusite
Al2SiO5IMA symbol: Andgrandfathered
Andalusite is a silicate mineral with the formula Al2SiO5, crystallizing in the orthorhombic system. It has a Mohs hardness of 7.5, typically brown, gray, green or red in color, with a vitreous luster, a specific gravity of 2.684. Its streak is red.
Photos
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Crystallography
| Crystal system | orthorhombic crystal systemWikidata (CC0) |
|---|---|
| Space group | P n n m |
| Cell (Å, °) | a = 7.7599, b = 7.8735, c = 5.544; α = 90, β = 90, γ = 90 |
| Cell volume | 338.725 ų, Z = 4 |
| Axial ratios | 0.9856:1:0.7041calculated from COD 9000919 |
| Source structure | COD 9000919 (American Mineralogist, 1984) — 1 of 18 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 5.527 | 4.511 | 2.763 | 4.533 | 1.483 | 3.914 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 86.9 | 69.9 | 64.6 | 48.8 | 46.8 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9000919; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.178 g/cm³calculated from COD 9000919 |
|---|---|
| Hardness (Mohs) | 7.5single sourceWikidata (CC0) 7.5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 2.684 g/cm3single sourceDana's System, 3rd Appendix (1915) |
| Color | brown, gray, green, red, rose, violetsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | whitesingle sourceWikidata (CC0) redsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 162.05 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Al 33.3%, Si 17.33%, O 49.37% |
Classification
| Nickel-Strunz (10th) | 9.AF.10Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.AF.10Wikidata (CC0) |
| Dana (8th) | 52.2.2b.1Wikidata (CC0) |