Chemical composition -- A hydrated aluminum phosphate with magnesium and iron.
Color --Blue.
Optics -- R.I. 1.62-1.68.
Durability -- Hardness 5.5-6. Brittle.
Crystal structure -- Monoclinic. Crystals are very rare and tiny.
Specific Gravity -- 3.08-3.38.
Sources --U.S., Bolivia, India, Brazil.
Lazulite (not to be confused with lazurite , or lapis lazuli) is not particularly abundant, especially in cuttable pieces. Fine quality pieces are rare, especially in sizes over a few carats. It can produce vivid, deep blue gems when found in suitable pieces.