Tectosilicate (framework silicate), sodalite group. Complete solid solution with nosean may exist, but is very limited with sodalite (Dana).
Specific gravity: 2.38 to 2.45
Hardness: 8 to 8½
Streak: Bright blue
Colour: Ultramarine, midnight blue, bluish green, green
Most lazurites analysed to date represent only sulfide-rich varieties of haüyne
and not a separate species (Mindt), so the information presented below may be more applicable to
haüyne than to lazurite.
Lazurite occurs as a contact metamorphic mineral in marble and skarn, and at pegmatite-limestone contacts, Also in some syenite and alkaline volcanics (Dana, HOM).
Associated minerals include calcite, pyrite, diopside, humite, forsterite, haüyne and muscovite (HOM, Mindat).
At the type locality, Ladjuar Medam, Sar-e Sang, Koksha Valley, Khash & Kuran Wa Munjan Districts, Badakhshan, Afghanistan, lazurite occurs in calcic skarn and marble (Mindat ). In the Koksha valley, lazurite pseudomorphs after muscovite have been found (KL p264).
Common impurities: Fe,Mg,K,H2O
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