Grandidierite
MgAl3O2(BO3)(SiO4)IMA symbol: Gddgrandfathered
Grandidierite is a silicate mineral with the formula MgAl3O2(BO3)(SiO4), crystallizing in the orthorhombic system. It has a Mohs hardness of 6-7, typically gray or green in color, a specific gravity of 3-4. Its streak is white.
Photos
Crystallography
| Crystal system | orthorhombic crystal systemWikidata (CC0) |
|---|---|
| Space group | P b n m |
| Cell (Å, °) | a = 10.325, b = 10.9575, c = 5.76; α = 90, β = 90, γ = 90 |
| Cell volume | 651.664 ų, Z = 4 |
| Axial ratios | 0.9423:1:0.5257calculated from COD 9010227 |
| Source structure | COD 9010227 (American Mineralogist, 2007) — 1 of 7 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 5.03 | 5.479 | 5.162 | 2.739 | 3.705 | 2.165 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 95.1 | 91.3 | 58.6 | 33.4 | 26.2 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9010227; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 2.945 g/cm³calculated from COD 9010227 |
|---|---|
| Hardness (Mohs) | 6-7single sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922) |
| Specific gravity | 3-4 g/cm3single sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922) |
| Color | gray, greensingle sourceFord, Dana's Textbook of Mineralogy, 3rd ed. (1922) |
| Streak | whitesingle sourceWikidata (CC0) |
Chemistry (calculated)
| Molecular weight | 288.14 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Mg 8.44%, Al 28.09%, O 49.97%, B 3.75%, Si 9.75% |
Classification
| Nickel-Strunz (10th) | 9.AJ.05Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.AJ.05Wikidata (CC0) |