Light play with feldspar

Feldspar comes in a lovely variety of stones: moonstone, labradorite, orthoclase, amazonite, sunstone, and spectrolite.

Moonstone displays adularescence, a blue-white opalescence which is a result of light interference with the layered structure of the stone.  The most striking example of this is in rainbow moonstone.

Similar yet different, labradorite  and spectrolite display labradorescence, “iridescence in metallic hues, called schiller” [1] with blue and green colors commonly seen, although this effect occurs in all colors.

Pink moonstone and sunstone can also display asterism, typically with four rayed stars.

With all the varieties and colors, feldspar is one of my favorite minerals!

Oregon schiller sunstone
Oregon schiller sunstone. Gorgeous copper hues!

[1]  Gemstones of the World: Newly Revised & Expanded Fourth Edition by Walter Schumann, p.53

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Stars in stones – asterism

Asterism is a term which describes “the effect of light rays forming a star (Latin aster, star)…It is usually created through reflection of light by thin fibrous or needle-like inclusions that lie in various directions.” [1]

Stars in gemstones may have four, six, or (less frequently) twelve rays.  With these stones, the angle of the stone to a light source is important to be able to see the star.  Natural gemstones known to exhibit asterism include:

Star ruby with six-rayed star
Star ruby with six-rayed star. One of the lovely stones in our collection at Dragon Dreams Jewelry, LLC.
  • star sapphire
  • star ruby
  • star diopside
  • star rose quartz
  • star blue quartz
  • star garnet
  • star spinel

[1]  Gemstones of the World: Newly Revised & Expanded Fourth Edition by Walter Schumann, p.52