Fermiite
Rare uranium mineral
From Wikipedia, the free encyclopedia
Fermiite is a rare uranium mineral with the formula Na4(UO2)(SO4)3·3H2O.[4] Chemically related minerals include oppenheimerite, meisserite (which is also structurally-related to fermiite),[3] belakovskiite, natrozippeite and plášilite.[5][6][7][8][9] Fermiite comes from the Blue Lizard mine, San Juan County, Utah, USA, which is known for many rare uranium minerals.[2][3][10] The name honors Enrico Fermi (1901–1954).[3]
| Fermiite | |
|---|---|
| General | |
| Category | Sulfate mineral |
| Formula | Na4(UO2)(SO4)3·3H2O |
| IMA symbol | Fmi[1] |
| Crystal system | Orthorhombic |
| Crystal class | Pyramidal (mm2) H-M symbol: (mm2) |
| Space group | Pmn21 |
| Unit cell | a = 11.84, b = 7.87 c = 15.33 [Å] (approximated); Z = 4 |
| Identification | |
| Color | Pale greenish-yellow |
| Crystal habit | prismatic |
| Cleavage | None |
| Tenacity | Brittle |
| Mohs scale hardness | 2.5 |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 3.31 (calculated); 3.23 (measured) |
| Optical properties | Biaxal (+) |
| Refractive index | nα=1.52, nβ=1.53, nγ=1.57 (approximated) |
| Pleochroism | Colourless (X & Y), pale greenish-yellow (Z) |
| 2V angle | 50o (calculated) |
| Other characteristics |  Radioactive |
| References | [2][3] |
Association
Fermiite is closely associated with numerous other sulfate minerals: oppenheimerite, bluelizardite, wetherillite, blödite, manganoblödite, chalcanthite, epsomite, gypsum, hexahydrite, kröhnkite, sideronatrite and tamarugite.[4]
Crystal structure
The main building block of the crystal structure of fermiite is a chain of the composition (UO2)(SO4)3. Chains are connected with five types of Na-O polyhedra.[4]