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LAPIS LAZULI

Introduction:  Lapis lazuli is a rock composed of lazurite, calcite and pyrite.  It may also contain hauyne, sodalite and nosean with small amounts of diopside, augite, mica and hornblende.  Pictured above is a rough piece from Badakhshan, Afghanistan weighing 180 grams and a matched pair of "tongue" cabochons weighing 15.19 ct.

Colors:  semitranslucent to opaque, medium to dark greenish blue to purplish blue, often veined or flecked with brassy colored pyrite and/or white calcite

Stone Sizes:  Rough blocks of material can be in excess of 100 kg.  Lapis lazuli is typically cut as carvings, cabochons, beads, inlays or tablets.

Localities:
-Badakhshan, Afghanistan: source of the finest lapis and among the oldest operating mines in the world (over 7000 years).  

-Chile:  gray and blue mixture from the Andes but the color is inferior to the Afghan material

-Mongolia:  light blue lapis with pyrite flecks

Treatments:
-Commonly dyed (D) to improve color and hide calcite.  

-It is also commonly impregnated or oiled (O) with paraffin or oil to make the polish appear better and also to seal the dye.

Gemology:
-Refractive Index:  vague readings around 1.50 and sometimes 1.67 (due to calcite)

-Birefringence:  None

-Optic Character:  AGG, if not opaque

-Specific Gravity:  2.75 (+/-0.25), varies depending on mineral content

-Hardness:  5 to 6; varies with impurities

-Toughness:  fair

-Chemical Composition:  varies with mineral content

-Cause of Color:  sulfur related color centers

-Fluorescence:  weak to moderate green or yellowish-green (SW); calcite inclusions may fluoresce pink (LW)

-Absorption Spectra:  not diagnostic

-Cleavage:  None

-Phenomena:  None

Name:  Lapis lazuli is from the Persian word, lazhward, meaning blue.

Dates:  It was an old birthstone for the month of December up until 1958 and is the gem for the 9th wedding anniversary.

Care:  The ultrasonic is risky and the steam cleaner should never be used.  Warm, soapy water is safe.


To see available lapis lazuli, click here.