Use as a Gem and Ornamental Material
Lapis lazuli is most widely known for its use as a gemstone. It is a popular material for cutting into cabochons and beads. It is also used in inlay or mosaic projects and often as a material for small sculptures. These uses made lapis the most popular opaque blue gemstone.
Although personal preferences vary, the most popular lapis has a uniform, deep blue to violet blue color. Many people enjoy a few randomly placed grains of gold pyrite or a few fractures or mottles of white calcite. However, when pyrite or calcite is present in more than minor amounts, the desirability of the material and the value are significantly lowered. Gray inclusions or mottling also quickly lowers desirability.
Lapis lazuli has some durability problems that limit its suitability for certain uses. Lapis has a Mohs hardness of about 5, which makes it very soft for use in a ring, cuff links or bracelet – especially if the top of the stone is raised above the top of the setting or bezel. In these uses, lapis will show signs of abrasion with continued use.
Lapis is best used in earrings, pins, and pendants, where abrasion is less likely to occur. When stored as unmounted stones or in jewelry, lapis can be damaged if the pieces are not isolated from one another. Jewelry is best stored in separate boxes or bags, or in trays with separate compartments for each item. Loose cut stones should be stored in separate papers, in bags, or in gem containers where the stones will not rub or abrade one another.
Treatment of Lapis Lazuli
Lapis lazuli is frequently treated after it is cut and before it is sold as finished gemstones, sculptures, or ornaments. Lapis lazuli is slightly porous and that allows it to accept and hold dye. Much of the material that enters the market has been treated with a blue dye to remove the visibility of white calcite. It is then frequently treated with wax or oil that improve the luster of polished surfaces and seal the dyed calcite.