Moonstone is popular and most prized of the Plagioclase Feldspar Group and has been used as a semi-precious stone.  Oligoclase is a member of the Plagioclase Feldspar Group. Oligoclase definition must contain 90-70% sodium to 10-30% calcium in the sodium/calcium position of the crystal structure. The various plagioclase feldspars are identified from each other gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements.

Popularly known under the names of sunstone and moonstone; Sunstone has flashes of reddish color caused inclusions of hematite and Moonstone shows a glowing shimmer similar to labradorescence, but lacking in color. The display is produced from lamellar intergrowths inside the crystal.  Adularescence is the moving "cloud of light" effect of Moonstone and Mineralogist calls it "schiller" which is caused tiny crystals of Albite arranged in layers within the stone.  A ray of light entering a layer and being refracted back and forth deeper layers before it exits the crystal causes the resulting shimmer effect. This refracted ray has a different character than when it went in and produces the moonlike glow.

Name:

Moonstone is also known as Adularia; the word was derived from Mount Adula, near St. Gotthard, Switzerland

History, Myth, Legend & Lore:

Pliny, Roman Historian - state that the "shining with a yellow luster from a colorless ground containing the image of the moon, if true daily waxes and wanes according to the state of the luminary".

Marbodus - believes the same phenomenon and adds the ability of the stone to mimic the phases of the moon, which was considered a sacred sign.

Antoine Mizauld (16th century writer)- performed experiments with a moonstone owned Pope Leo X (1475 - 1521).  He recorded the changing size and position of a point of light in the stone and concluded a direct correspondence existed to the lunar cycle.

India - moonstone was considered a sacred stone and thought to bring good fortune and remained a prized gift for lovers.  It arouses passions and gave lovers the power to see their future together.  The stone was said to ease childbirth, enhances fertility, promotes pregnancy, relieves menstrual discomfort and increases lactation.

Modern Gem Therapy Practitioners - serves as a tool to enhance feminine energy and to heal emotional distress and brings calmness.  Used to treat degenerative conditions of the skin, hair, eyes and fleshy organs.