| Ferrimolybdite | |
| Category: | Molybdate mineral |
| Formula: | Fe3+2(MoO4)3·8(H2O) or Fe3+2(MoO4)3·n(H2O) |
| Imasymbol: | Fmyb[1] |
| Strunz: | 7.GB.30 |
| System: | Orthorhombic |
| Class: | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Symmetry: | Pmmn |
| Unit Cell: | a = 6.665, b = 15.423 c = 29.901 [Å]; Z = 8 |
| Color: | Canary-yellow, straw-yellow, greenish yellow |
| Habit: | Acicular tufted to radial aggregates; powdery, earthy |
| Cleavage: | Distinct on |
| Fracture: | Uneven |
| Mohs: | 1-2 |
| Luster: | Adamantine, silky, earthy |
| Streak: | Light yellow |
| Diaphaneity: | Transparent to translucent |
| Gravity: | 2.99 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.720 - 1.810 nβ = 1.730 - 1.830 nγ = 1.850 - 2.040 |
| Birefringence: | δ = 0.130 - 0.230 |
| Pleochroism: | X = Y = clear to nearly colorless; Z = dirty gray to canary-yellow |
| 2V: | 26° to 32° (calculated) |
| References: | [2] [3] [4] |
Ferrimolybdite is a hydrous iron molybdate mineral with formula: Fe3+2(MoO4)3·8(H2O)[3] or Fe3+2(MoO4)3·n(H2O).[2] It forms coatings and radial aggregates of soft yellow needles which crystallize in the orthorhombic system.
It was first described in 1914 for an occurrence in the Alekseevskii Mine in the Karysh River Basin, Khakassia Republic, Siberia, Russia.[2] It was named for its composition (ferric iron and molybdenum).
It occurs as an oxidation product of molybdenum bearing ore deposits. Associated minerals include: molybdenite, pyrite and chalcopyrite.[3]