Lazurite

Lazurite is a deep‐blue to greenish‐blue. The colour is due to the presence of Trisulfur#Radical anion| anions. It has a Mohs hardness of 5.0 to 5.5 and a specific gravity of 2.4. It is translucent with a refractive index of 1.50. It is fusible at 3.5 on Wolfgang Franz von Kobell's fusibility scale, and soluble in HCl. It commonly contains or is associated with grains of pyrite. Lazurite is a product of contact metamorphism of limestone and is typically associated with calcite, pyrite, diopside, humite, forsterite, hauyne and muscovite. It is also mined at Lake Baikal in Siberia; Mount Vesuvius; Burma; Canada; and the United States. The most important mineral component of lapis lazuli is lazurite.{{Cite web|url=https://www.mindat.org/min-2330.html == Redefinition ==

Most lapis lazuli gets its blue color from Hauyne and almost none contain "true lazurite". == Structure ==

Lazurite and hauyne seem to have the same structure and both are sulfate-dominant minerals. Lazurite is a pigment (opalescent) and has a bright blue streak (especially as a component of the semiprecious stone lapis lazuli). Many hauynes have a white or pale blue streak and are translucent. The difference might be a consequence of the redox state (sulfate to sulfide ratio). ==See also==