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Opal - The Stunning October Birthstone

Opal is the accepted birthstone but definitely not the only one! For the calendar month of October the birthstones also include tourmaline, jasper, aquamarine, coral and beryl. Two Zodiac signs also span October, allowing those born under the signs of Libra (Sept. 23-Oct 23) and Scorpio (Oct 24-Nov 22) to include peridot, sapphire, lapis, agate, topaz, garnet, ruby and amethyst. How about that - all our favorites in one "month"!!

Precious opal shows a variable play of internal color dictated by its internal structure. The silica spheres of which opal is composed are arranged in a close packed lattice which cause light to be diffracted through the structure. If the packing of spheres is tight color play may be slight, and if the spheres are larger and the packing is not so snug more play of color is seen. (This is a vastly simplified explanation.) Australia produces 97% of the worlds opal. The most famous site is the town of Coober Pedy. Mintabie Opal Fields produces the rarer black opal as well as the crystal type usually found in Coober Pedy. Andomooka (So. Australaia) is also a major producer of matrix opal, crystal opal and black opal. Boulder opal is that found in concretions and ironstone. Also many types of opalized fossil remains are found—including tree roots, marine creatures and dinosaur bones.

The Virgin Valley opal fields of Humboldt Co. in Nevada are famous for the black, crystal, white, fire and lemon opal. Some of the opal has a high water content and may dry and crack.. Anointer source of white base opal is the Spencer Mine is Idaho.

There are also many kinds of common opal, and other varieties include fire opal. The most famous site is in Mexico in the state of Queretaro. They display green flashes and are usually faceted. Without color play they may be called jelly opals. I hope you all saw the article in Rock and Gem this month about the opal from Ethiopia.

The name of opal is from the Roman term opalus adapted from the Sanskrit word upala. The term first appears in Roman references about 250 B.C. when the stone was valued above all others. At that time it is supposed that opal was coming from India.

During the Middle Ages opal was thought to provide great luck as it was supposed to have all the virtues of each gemstone whose color could be seen in the colors of the opal. It was also said to make a person invisible if wrapped in a fresh bay leaf and held in the hand! After Sir Walter Scott published his book Anne of Geierstein in 1829 it's reputation took a dive! In the book Anne wears an opal with supernatural powers and when a drop of holy water fell on it it turns into a colorless stone and Anne dies shortly thereafter. Because the book was such a hit! people began to associate opals with bad luck and the sale of the stone dropped by 50%! (The power of the written word and superstition.) Even in the 20th century it retained a reputation as possessing the "evil eye".