Lazurite

minerals

humite

forsterite

hauyne

Formula: Na3Ca(Si3Al3)O12S
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
Environments

Igneous environments
Metamorphic environments

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).

Localities

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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