Brookite
TiO2IMA symbol: Brkgrandfathered
Brookite is an oxide or hydroxide mineral with the formula TiO2, crystallizing in the orthorhombic system. It has a Mohs hardness of 5.5-6, typically black, brown, red or yellow in color, with an adamantine or metallic luster, a specific gravity of 3.87-4.01. Its streak is gray or red.
Photos
Crystallography
| Crystal system | orthorhombic crystal systemWikidata (CC0) |
|---|---|
| Space group | P b c a |
| Cell (Å, °) | a = 9.174, b = 5.449, c = 5.138; α = 90, β = 90, γ = 90 |
| Cell volume | 256.844 ų, Z = 8 |
| Axial ratios | 1.6836:1:0.9429calculated from COD 9004137 |
| Source structure | COD 9004137 (The Canadian Mineralogist, 1979) — 1 of 5 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 2.898 | 3.509 | 3.462 | 1.66 | 1.891 | 1.689 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 99.4 | 78.4 | 36.4 | 35.5 | 25.2 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9004137; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 4.131 g/cm³calculated from COD 9004137 |
|---|---|
| Hardness (Mohs) | 5.5-6single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.87-4.01 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | black, brown, red, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | gray, red, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | adamantine, metallic, submetallicsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 79.87 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Ti 59.93%, O 40.07% |
Classification
| Nickel-Strunz (10th) | 4.DD.10Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 4.DD.10Wikidata (CC0) |
| Dana (8th) | 4.4.5.1Wikidata (CC0) |