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An opalescent mineral that is used as a Gemstone. Sunstones are translucent stones with an iridescent sheen due to the parallel arrangement of its crystals. They are usually a golden-brown with dark red hematite flakes. The iron oxide inclusions give the stone a reddish glow. Major deposits of sunstones occur in Norway (Tvedestrand), Russia (near Lake Baikal), and the U.S. (Pennsylvania, North Carolina). Moonstones are found in potassium (Orthoclase) feldspars, while Plagioclase feldspars (albite, oligoclase, or Labradorite) produce sunstones.

Physical and Chemical Properties

Triclinic prismatic crystals. Inclusions give spangled appearance.

Mohs Hardness 6.0 - 6.5
Density 2.56-2.76 g/ml
Refractive Index 1.53-1.59


Properties of Common Gemstones

Resources and Citations

  • R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997