Topaz
Al2SiO4F2IMA symbol: Tpzgrandfathered
Topaz is a silicate mineral with the formula Al2SiO4F2, crystallizing in the orthorhombic system. It has a Mohs hardness of 8, typically white, gray, green or red in color, with a vitreous luster, a specific gravity of 5.4. Its streak is red.
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Crystallography
| Crystal system | orthorhombic crystal systemWikidata (CC0) |
|---|---|
| Space group | P b n m |
| Cell (Å, °) | a = 4.6601, b = 8.826, c = 8.3778; α = 90, β = 90, γ = 90 |
| Cell volume | 344.579 ų, Z = 4 |
| Axial ratios | 0.5280:1:0.9492calculated from COD 9010122 |
| Source structure | COD 9010122 (American Mineralogist, 2006) — 1 of 12 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 2.938 | 3.204 | 3.698 | 2.105 | 2.36 | 1.357 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 80.8 | 69.2 | 59.3 | 48.7 | 42.5 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9010122; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.548 g/cm³calculated from COD 9010122 |
|---|---|
| Hardness (Mohs) | 8single sourceWikidata (CC0) 8single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 5.4 g/cm3single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Color | gray, green, red, white, yellowsingle 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 | 184.04 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Al 29.32%, Si 15.26%, O 34.77%, F 20.65% |
Classification
| Nickel-Strunz (10th) | 9.AF.35Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.AF.35Wikidata (CC0) |