| Simpsonite | |
| Category: | Oxide minerals |
| Imasymbol: | Spn[1] |
| Molweight: | 813.65 g/mol |
| Strunz: | 4.DC.10 |
| System: | Trigonal |
| Class: | Pyramidal (3) H-M symbol: (3) |
| Symmetry: | P3 |
| Unit Cell: | a = 7.37, c = 4.51 [Å]; Z = 1 |
| Color: | White to cream, yellow to yellow-brown when altered |
| Habit: | Euhedral, prismatic, striated |
| Cleavage: | None |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Mohs: | 7–7.5 |
| Luster: | Vitreous to adamantine |
| Refractive: | nω = 2.045 nε = 2.025 |
| Opticalprop: | Uniaxial negative |
| Birefringence: | δ = 0.020 |
| Streak: | White |
| Gravity: | 6.7 |
| Diaphaneity: | Semitransparent |
| Other: | Blue-white cathodoluminescence and yellow fluorescence in SW UV |
| References: | [2] [3] [4] [5] |
Simpsonite has a general formula of . It occurs as euhedral to subhedral tabular to short and prismatic crystals, commonly in subparallel groups. Under the petrographic microscope it has a very high relief.
Discovered in 1938, it was named after Edward Sydney Simpson (1875–1939), government mineralogist and analyst of Western Australia.[4] It is an accessory mineral in some tantalum-rich granite pegmatites. It occurs in association with tantalite, manganotantalite, microlite, tapiolite, beryl, spodumene, montebrasite, pollucite, petalite, eucryptite, tourmaline, muscovite and quartz.[2] It is found in a few locations around the world, notably in the Onca and Paraíba mines of Rio Grande do Norte, Brazil and at Tabba Tabba, Western Australia.[2]