Avogadrite
Avogadrite ((K,Cs)BF4) is a potassium-caesium tetrafluoroborate in the halide class. Avogadrite crystallizes in the orthorhombic system (space group Pnma) with cell parameters a 8.66 Å, b 5.48 Å and c Å 7.03.
| Avogadrite | |
|---|---|
Ferruccite (white) on avogadrite (yellow-brownish), picture size: 5 mm | |
| General | |
| Category | Halide mineral |
| Formula (repeating unit) | (K,Cs)BF4 |
| IMA symbol | Avg |
| Strunz classification | 3.CA.10 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnma |
| Unit cell | a = 8.6588, b = 5.48 c = 7.0299 [Å]; Z = 4 |
| Identification | |
| Color | Colorless to white, yellowish to reddish |
| Crystal habit | Tabular to platy octagonal crystals, tiny crystals, elongate |
| Luster | Vitreous, greasy |
| Diaphaneity | Translucent |
| Specific gravity | 2.9 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.3239, nβ = 1.3245, nγ = 1.3247 |
| Birefringence | δ = 0.001 |
| 2V angle | 75°(meas), 58° (calc) |
| Other characteristics | Bitter taste |
| References | |
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