In addition to lazurite, specimens of lapis lazuli usually contain calcite and pyrite. Sodalite, hauyne, wollastonite, afghanite, mica, dolomite, diopside, and a diversity of other minerals might also be present. To be called “lapis lazuli,” a rock must have a distinctly blue color and contain at least 25% blue lazurite.

Calcite is often the second most abundant mineral present in lapis lazuli. Its presence can be very obvious, appearing as white layers, fractures, or mottling. It can also be finely intermixed with lazurite to produce a rock with a faded denim color.

Pyrite usually occurs in lapis lazuli as tiny, randomly spaced grains with a contrasting gold color. When abundant, the grains can be concentrated or intergrown into distinct layers or patches. It can occasionally occur as a fracture-filling mineral.

As a rock, lapis lazuli is composed of several minerals, each with its own hardness, cleavage/fracture characteristics, specific gravity, and color. Hardness ranges from a Mohs 3 for calcite to the 6.5 of pyrite. The hardness of the material depends upon where you test it.

Physical Properties of Lapis Lazuli
Classification	A metamorphic rock that contains enough of the mineral lazurite to impart a distinct blue color. It may also contain significant amounts of calcite, pyrite, and minor amounts of other minerals.
Color	Blue. Often with white calcite veining or mottling, and gold grains of pyrite.
Streak	Blue.
Luster	Dull, but polishes to a bright luster.
Diaphaneity	Semi-translucent to opaque.
Cleavage	None, though it may split easily along foliation or calcite veins and layers.
Mohs Hardness	Varies between the 3 of calcite and the 5 to 5.5 of lazurite. Not well suited for use as a ring stone or in bracelets.
Specific Gravity	2.7 to 2.9 or more depending upon the amount of pyrite
Diagnostic Properties	Blue color, association with pyrite, and hardness.
Uses	Cabochons, beads, carvings, spheres, inlay, and pigments.