Lapis lazuli gemstone

by Manisha G

lapis-lazuli-gemstoneThis stone is characterised by its beautiful colour, which in best specimens is a uniform dark blue of great intensity. Paler tints are common and stones are often mottled. Specimens usually contain brassy spangles of iron pyrites.

Characteristics: It is really a rock; a mixture of different minerals (a) hauynite, (b) calcite, (c) sodalite; iron pyrites may or may not be included. Colour depends chiefly on the presence of hauynite. The matrix is calcite, in which are embedded numerous grains of the above substances. Lapis-lazuli is opaque and hence is scarcely ever faceted.

S.G. variable, but usually near 2.8 (2.7 to 2.90) higher when pyrite is present. “Swiss Lapis” (stained Jasper) has lower S.G., more vitreous lustre and lacks the specks of iron pyrites. Hardness is 5.50, mean R.I. 1.50.

A synthetic Lapis Lazuli is now made and is very much like the natural material and only sophisticated tests can distinguish the two.

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