Lapis lazuli

Lapis is a semi-precious gemstone, known and used as far back as Pharonic Egypt. It is a compound of various other minerals and, in its finest form is intense radiant blue, occasionally with golden pyrite flecks. It takes excellent polish and has been widely used for jewellery, and in mosaics. Ground, it is a major constituent in the pigment Ultramarine.

Accordingly it is a period stone, and was available in medieval Europe.

Lapis is somewhat soft for a gemstone (5 - 6 on the Mohs scale). Nevertheless it is highly popular even today. It has an indistinct cleavage, which makes it suitable for ring stones when cut en cabochon or in bufftop. Lapis lazuli is also widely used in beads, small sculpture, and other ornamental objects.

References:

• Walter Schumann, Gemstones of the World, New York, 1997
  
• June Culp Zeitner, Gem & Lapidary Materials, Geoscience Press, 1996