Birthstone Gems

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October Birthstone - Opal

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Opal fact file

Crystal Structure: octahedrons
Chemical Composition: Quartz - Silicon dioxide, SiO2
Hardness: 5 ½ to 6 ½ MOHS

Refractive Index: 1.43-1.46
Colors: Body color - white or tan or bluish.
Play colors - red, orange, yellow, blue, green etc

Opal and Tourmaline are the October birthstones. Opal is a gem of many colors.

This gem of sedimentary silica has grids of silica spheres which show a play of colors created thru diffraction. The size of the spheres determine the wavelengths and therefore the colors seen. The brilliance of the colors are determined by the regularity of the grid. These changing colors of opal has been used by literateurs down the ages, from Shakespeare onwards, to symbolize a shifting mind and unsteadiness. There is a superstition that suggests that it is bad luck to wear an opal if opal is not your birthstone. Opals can deteriorate and change from a highly colorful, somewhat glassy stone to a rather colorless mass of a chalky silicon dioxide. That is because opals are unstable and are just one of the phases through which gel-like silica (SiO2) can pass on its way to becoming stable crystalline quartz.

Related Pages:

Opal Properties
Know more about the physical and chemical properties of Opal such as composition, color etc.
Opal History and Geography
Some interesting facts about Opal such as where it is found, stories from history and mythology, and its healing properties.
Buying and Caring for Opal Jewelry
Tips for Buying Opal Jewelry and taking care of Opal Jewelry