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Moonstone Information
Moonstone is an opalescent variety of the potassium feldspar adularia.
See also our other feldspar varieties:
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MOONSTONE PHYSICAL PROPERTIES
- Moonstone Chemical Composition: KAlSi3O8
- Class: tektosilicate
- Crystal system: monoclinic; 2/m
- Crystal habit: pseudo-orthorhombic prismatic crystals
- Twinning: twinned according to the Carlsbad twin law, and the baveno and manebach twin laws.
- Specific gravity: 2.56
- Index of refraction: 1.52
- Birefringence: weak maximum birefringence of 0.005
- Pleochroism: colorless in section
- Hardness: 6
- Color: colorless, usually with bluish sheen, although the sheen can be green, gold or multi-color (known as rainbow moonstone)
- Luster: vitreous
- Transparency: semi-translucent to semi-transparent
- Cleavage: perfect cleavage on {001}
- Fracture: conchoidal
- Streak: white
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FELDSPAR (moonstone) BACKGROUND INFORMATION
Moonstone is a variety of orthoclase feldspar. In the earth's crust, feldspars are more abundant than all other minerals combined. The majority of the common feldspars fall into two groups, the alkali feldspars (KAlSi3O8 through NaAlSi3O8 series), and the plagioclase feldspars (NaAlSi3O8 through CaAl2Si2O8 series). Orthoclase (KAlSi3O8) is the medium temperature pure potassium end member of the alkali feldspar group.
At high temperatures, the alkali feldspars form a continuous
solid solution series, however at medium to low crystalization
temperatures the sodium feldspar (albite) and potassium feldspar
(microcline or orthoclase) separate forming lattice type exsolution
intergrowths, usually as thin layers of albite roughly parallel to
{100} in a host crystal of microcline or orthoclase. This is known
as perthitic texture.
Adularia is an unusual gem variety of the
potassium feldspar orthoclase. It exhibits an iridescence named
adularescence (popularly known as moonstone) which is clearly visible in our samples of
moonstone jewelry. This iridescence is due to diffused light reflection
from microscopic parallel intergrowths of albite within the orthoclase.
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MOONSTONE OCCURRENCE AND DIAGNOSTIC FEATURES
Moonstone is iridescent orthoclase feldspar. The iridescence in moonstone is due to diffused light reflection from microscopic parallel intergrowths of albite felspar within the orthoclase.
Orthoclase commonly occurs in plutonic igneous rocks such as granites, granodiorites, and syenites that cooled at relatively fast rates and at moderate depth as compared to microcline which forms in more slowly cooled rocks.
Orthoclase is distinguished from the other feldspars by its right angle cleavage and the lack of twin striations on the best cleavage surface. In the field the indicators are its color, hardness, and cleavage. Moonstone is easily recognized by its play of colors.
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MOONSTONE HISTORICAL INFORMATION AND USES
The name moonstone comes quite simply from the fact that it can resemble closely the white opaque look of our moon. Feldspar is derived from the German word feld which means field.
Moonstone is a sacred stone in India. It is believed to bring good fortune, and to give protection against the dangers of travel. It is thought to be especially powerful in arousing passion and desire.
Moonstone is used as an ornamental lapidary material.
The astrological sign of moonstone are cancer, Libra, and scorpio.
The astrological sign of amazonite is Virgo.
Amazonite is a alternate birthstone for the month of June.
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MOONSTONE METAPHYSICAL PROPERTIES
Moonstone is said to enhance perception and to alleviate emotional tension while stimulating compusure and confidence, and to improve one's ability to handle difficult situations.
Moonstone is also said to help rejuvenate the body and to calm the mind, bringing a deep sense of happiness. It also is said to enhance fertility and to help with ease of pregnancy and childbirth.
For more in-depth metaphysical information, see our Metaphysical Books section.
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