Lazulite Explained

Lazulite
Category:Phosphate mineral
Imasymbol:Lzl[1]
Strunz:8.BB.40
System:Monoclinic
Class:Prismatic (2/m)
(same H–M symbol)
Symmetry:P21/c
Unit Cell:a = 7.144(1), b = 7.278(1)
c = 7.228(1) [Å]; β = 120.5(1)°; Z = 2
Color:Azure, sky blue, bluish white, yellow-green, blue-green, rarely green
Habit:Tabular, acute to stubby bipyramidal crystals; granular, massive
Twinning:Common by several twin laws
Cleavage:Poor to good on, indistinct on
Fracture:Uneven, splintery
Tenacity:Brittle
Mohs:5.5–6.0
Luster:Vitreous
Streak:White
Diaphaneity:Transparent to translucent to nearly opaque
Gravity:3.122–3.240
Opticalprop:Biaxial (−)
Refractive: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:Measured: 61–70°
Fusibility:Infusible
Solubility:Insoluble

Lazulite is a transparent to semi-opaque, blue mineral that is a phosphate of magnesium, iron, and aluminium, with the chemical formula . Lazulite forms one endmember of a solid solution series with the darker, iron-rich scorzalite.

Lazulite crystallizes in the monoclinic system. Its crystal habits include steep bipyramidal or wedge-shaped crystals.[2] Lazulite has a Mohs hardness of 5.5–6.0 and a specific gravity of 3.0–3.1. It is infusible and insoluble.[3]

Occurrence and discovery

Lazulite forms by high-grade metamorphism of silica-rich rocks and in pegmatites. It occurs inassociation with quartz, andalusite, rutile, kyanite, corundum, muscovite, pyrophyllite,dumortierite, wagnerite, svanbergite, trolleite, and berlinite in metamorphic terrains; and with albite, quartz, muscovite, tourmaline and beryl in pegmatites.It may be confused with lazurite, lapis lazuli or azurite.

The type locality is in Freßnitzgraben in Krieglach, it's also found in Salzburg, Austria; Zermatt, Switzerland; Minas Gerais, Brazil; Lincoln County, Georgia; Inyo County, California; the Yukon in Canada; and elsewhere.

It was first described in 1795 for deposits in Styria, Austria. Its name comes from the German German: lazurstein, for 'blue stone'[4] or from the Arabic for heaven.[3]

Notes and References

  1. Warr. L. N. . 2021 . IMA–CNMNC approved mineral symbols . . 85 . 3 . 291–320 . . 10.1180/mgm.2021.43 . 2021MinM...85..291W . 235729616 . free.
  2. Web site: Lazulite . Minerals.net.
  3. Book: Hurlbut. Cornelius S. . Klein. Cornelius . 1985 . Manual of Mineralogy . 20th . . 0-471-80580-7.
  4. Web site: Lazulite . Handbook of Mineralogy . RRUFF . live . https://web.archive.org/web/20210705152731/https://rruff.info/doclib/hom/lazulite.pdf . Jul 5, 2021 .