Sellaite
MgF2IMA symbol: Selgrandfathered
Sellaite is a halide mineral with the formula MgF2, crystallizing in the tetragonal system. It has a Mohs hardness of 5, typically colorless in color, with a vitreous luster, a specific gravity of 2.972-5. Cleavage is perfect.
Photos
Crystallography
| Crystal system | tetragonal crystal systemWikidata (CC0) |
|---|---|
| Space group | P 42/m n m |
| Cell (Å, °) | a = 4.623, b = 4.623, c = 3.052; α = 90, β = 90, γ = 90 |
| Cell volume | 65.228 ų, Z = 2 |
| Axial ratios | 1.0000:1:0.6602calculated from COD 9009075 |
| Source structure | COD 9009075 (Crystal Structures, 1963) — 1 of 3 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 3.269 | 2.231 | 1.712 | 1.376 | 1.634 | 2.067 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 87.5 | 76.5 | 40.6 | 29.9 | 28.3 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9009075; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.172 g/cm³calculated from COD 9009075 |
|---|---|
| Hardness (Mohs) | 5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 2.972-5 g/cm3single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Color | colorlesssingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Cleavage | perfectDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 62.3 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Mg 39.01%, F 60.99% |
Classification
| Nickel-Strunz (10th) | 3.AB.15Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 3.AB.15Wikidata (CC0) |