|Chemical composition||rock consisting of lazurite, hauyne, calcite and pyrite|
|Refractive index||1.500 - 1.670|
|Specific gravity||2.50 - 3.00|
|Lustre||resinous to vitreous|
Lapis lazuli is not a mineral, but a rock consisting of as many as 15 different minerals. It is a contact metamorphic rock with variable composition and varying physical properties, usually forming as the result of contact metamorphism of limestones. The primary minerals present in lapis are lazurite, hauyine, diopside, calcite and pyrite. In Egypt, lapis beads, carvings, scarabs and jewelry date back over 5000 years!
Lapis lazuli was being mined in the Badakhshan province of Afghanistan as early as the 3rd millennium BC, and there are sources that are found as far east as in the region around Lake Baikal in Siberia. Trade in the stone is ancient enough for lapis jewelry to have been found at Predynastic Egyptian and ancient Sumerian sites, and as lapis beads at neolithic burials in Mehrgarh, the Caucasus, and even as far from Afghanistan as Mauritania.
In addition to the Afghan deposits, lapis has been extracted for many years in the Andes (near Ovalle, Chile), the Lake Baikal region of Russia; Siberia; Angola; Argentina; Burma; Pakistan; Canada; India; and in the USA in California and Colorado.
G&G Articles on Lapis Lazulu 1934-1980
- Spring 1936, The specific gravity of lapis lazuli, p. 8, 1p.
- Summer 1941, Colorado Lapis Lazuli, p. 154, 3pp.
- Fall 1954, A New Substitute for Lapis Lazuli, by Anderson, p. 88, 2pp.
- [http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/summer-1962.pdf Summer 1962, A lapis lazuli test, p. 315, 1p.
- Spring 1963, Translucent lapis lazuli (showing absorption spectrum), p. 20, 1p.
- Summer 1963, Testing stained lapis lazuli, p. 44, 1p.
- Fall 1965, Notes on lapis lazuli and its treatment, p. 337, 2pp.
- Summer 1967, Dyed lapis lazuli, p. 180, 2pp.
- Spring 1968, Dyed waxed lapis lazuli, p. 278, 1p.
- Summer 1970, A beautiful Pietre Dure (Italian inlay) lapis lazuli, p. 188, 1p.
- Fall 1974, Imitation lapis lazuli, p. 327, 4pp.
- Fall 1976, Non-Single-Crystal Synthetics (synthetic Gilson lapis lazuli), by Nassau, p. 194, 5pp.