Astrophyllite
K2NaFe2+7Ti2(Si4O12)2O2(OH)4FIMA symbol: Astgrandfathered
Astrophyllite is a silicate mineral with the formula K2NaFe2+7Ti2(Si4O12)2O2(OH)4F, crystallizing in the triclinic system. It has a Mohs hardness of 3, typically yellow in color, with a metallic or pearly luster, a specific gravity of 3.3-3.4. Its streak is golden; cleavage is imperfect or perfect.
Photos
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Crystallography
| Crystal system | triclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | P -1 |
| Cell (Å, °) | a = 5.3857, b = 11.9072, c = 11.7105; α = 113.062, β = 94.614, γ = 103.098 |
| Cell volume | 660.878 ų, Z = 1 |
| Axial ratios | 0.4523:1:0.9835calculated from COD 9004710 |
| Source structure | COD 9004710 (The Canadian Mineralogist, 2003) — 1 of 9 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 10.581 | 3.527 | 10.513 | 2.776 | 2.779 | 2.579 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 25.2 | 18.8 | 16.9 | 16.1 | 15.2 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9004710; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.191 g/cm³calculated from COD 9004710 |
|---|---|
| Hardness (Mohs) | 3single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.3-3.4 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | yellowsingle sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922) |
| Streak | goldenDana, System of Mineralogy, 6th ed. (1892) |
| Luster | metallic, pearly, submetallicsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Cleavage | imperfect, perfectDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 9.DC.05Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.DC.05Wikidata (CC0) |