Lazulite
Lazulite ((Mg,Fe2+)Al2(PO4)2(OH)2) is a blue, phosphate mineral containing magnesium, iron, and aluminium phosphate. Lazulite forms one endmember of a solid solution series with the darker iron rich scorzalite.
| Lazulite | |
|---|---|
Lazulite, Near Rapid Creek, Yukon, Canada | |
| General | |
| Category | Phosphate mineral |
| Formula (repeating unit) | (Mg,Fe2+)Al2(PO4)2(OH)2 |
| IMA symbol | Lzl |
| Strunz classification | 8.BB.40 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/c |
| Unit cell | a = 7.144(1), b = 7.278(1) c = 7.228(1) [Å]; β = 120.5(1)°; Z = 2 |
| Identification | |
| Color | Azure-blue, sky-blue, bluish white, yellow-green, blue-green, rarely green |
| Crystal habit | Tabular, acute to stubby bipyramidal crystals; granular, massive |
| Twinning | Common by several twin laws |
| Cleavage | Poor to good on {110}, indistinct on {101} |
| Fracture | Uneven, splintery |
| Tenacity | Brittle |
| Mohs scale hardness | 5.5–6.0 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent to nearly opaque |
| Specific gravity | 3.122–3.240 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.604 – 1.626 nβ = 1.626 – 1.654 nγ = 1.637 – 1.663 |
| Birefringence | δ = 0.033 – 0.037 |
| Pleochroism | Strong: X = colorless, Y = blue, Z = darker blue |
| 2V angle | Measured: 61° to 70° |
| Fusibility | Infusible |
| Solubility | Insoluble |
| References | |
Lazulite crystallizes in the monoclinic system. Crystal habits include steep bipyramidal or wedge-shaped crystals. Lazulite has a Mohs hardness of 5.5 to 6 and a specific gravity of 3.0 to 3.1. It is infusible and insoluble.
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