| Lazulite | |
|---|---|
 Lazulite specimen found near Rapid Creek,Yukon, Canada | |
| General | |
| Category | Phosphate mineral |
| Formula | (Mg,Fe2+)Al2(PO4)2(OH)2 |
| IMA symbol | Lzl[1] |
| Strunz classification | 8.BB.40 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (sameH–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,sky blue, bluish white,yellow-green,blue-green, rarely green |
| Crystal habit | Tabular, acute to stubbybipyramidal 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 nearlyopaque |
| 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: 61–70° |
| Fusibility | Infusible |
| Solubility | Insoluble |
| References | [2][3][4][5] |
Lazulite orAzure spar[6]: 14 is a transparent to semi-opaque, bluemineral that is aphosphate ofmagnesium,iron, andaluminium, with thechemical formula(Mg,Fe2+)Al2(PO4)2(OH)2.[3] Lazulite forms oneendmember of asolid solution series with the darker, iron-richscorzalite.[3][5]
Lazulite crystallizes in themonoclinic system. Itscrystal habits include steepbipyramidal or wedge-shaped crystals.[7] Lazulite has aMohs hardness of 5.5–6.0 and aspecific gravity of 3.0–3.1. It is infusible and insoluble.[5]
Lazulite forms by high-grademetamorphism ofsilica-rich rocks and inpegmatites. It occurs inassociation withquartz,andalusite,rutile,kyanite,corundum,muscovite,pyrophyllite,dumortierite,wagnerite,svanbergite,trolleite, andberlinite in metamorphic terrains; and withalbite, quartz, muscovite,tourmaline andberyl in pegmatites.[2]It may be confused withlazurite,lapis lazuli orazurite.
Thetype locality is in Freßnitzgraben inKrieglach, it's also found inSalzburg,Austria;Zermatt,Switzerland;Minas Gerais,Brazil;Lincoln County, Georgia;Inyo County, California; theYukon inCanada; and elsewhere.
It was first described in 1795 for deposits inStyria,Austria.[3] Its name comes from the Germanlazurstein, for 'blue stone'[2] or from theArabic forheaven.[3][5]
