Modern & Carbochon Birthstone – Opal
Traditional Birthstone - Tourmaline
Zodiac Stones for October
Libra Sept. 23 – Oct. 23 Chrysolite (Peridot)
Scorpio Oct. 24 – Nov. 21 Aquamarine
OPAL - pronounced (ō‘pəl)
Opal is a relatively common mineral in its common form, which is known as common opal and lacks the play of color for which gem, or precious, opal is known. The hardness of opal on the Mohs hardness scale ranges from 5 to 6.
The color of common opal ranges from transparent, glassy, and colorless to white and bluish white. The luster of the stone can go from vitreous to pearly. Precious opal has a play of color that is the result of white light being diffracted by the relatively regular internal array of silica spheres. Semiprecious Opal is beautiful but it does not have the fire and brilliance of a precious opal. Because opal is a hydrous mineral, certain opals from specific geologic occurrences may crack because of water loss. Therefore, considerable care is required in the polishing and handling of opal.
The name opal probably is derived from the ancient names for the stone. Sanskrit; upala which translates “precious stone”, the Greek; opallios which translates “color change”, and the Latin; opalus which translates “stone from several elements”. It has been mined for centuries, at least since Roman times when they extracted the opal from areas now within the Czech Republic. The Aztecs made use of local Mexican sources as did the Spaniards when they exported the material back to Europe.
Australia produces around 97% of the world’s opal. 90% is called ‘light opal’ or white and crystal opal. White makes up 60% and all the opal fields produce white opal; Crystal opal or pure hydrated silica makes up 30%; 8% is black and only 2% is boulder opal.
A source of white base opal in the United States is Spencer, Idaho. A high percentage of the opal found there occurs in thin layers. As a result, most of the production goes into the making of doublets and triplets.
The state gem stone for Nevada is precious black opal, which is named for the true black opal found in Virgin Valley, Humboldt County, Nevada.
OTHER TYPES OF OPAL
Fire opal is a translucent to semi-opaque stone that is generally yellow to bright orange and sometimes nearly red and displays pleochroism at certain angles.
Peruvian opal is a semi-opaque to opaque stone found in Peru which is often cut to include the matrix in the more opaque stones. It comes in various shades of blue and pink.
African Opal is a semi-opaqie to opaque stone found in Africa. It is found in various shades of white, yellow and brown.
Tourmaline – pronounced: tour·ma·line (tʊr’mə-lĭn, -lēn’)
Tourmaline seems to have a special place in the hearts of mineral collectors as well as in that of gem and gemstone enthusiasts. Its nearly universal popularity is based on two very important facts: first, it is a bright and beautiful gemstone that can be found in just about any color; and second, materials that are of acceptable quality are affordable to most purchasers.
The word “rainbow” is used figuratively to describe tourmaline. In reality, it is a well recognized fact that tourmaline’s diversity in color is not limited to the seven colors of the rainbow. Tourmaline can be colorless to just about any color, hue, or tone known to man. And if range of colors among different tourmalines is not enough, individual crystals can vary in color along their length or in cross-section.
The variations in color along a crystal’s length give rise to the bicolor and tricolor tourmalines which have multitudes of color combinations. The variation in color in cross-section can be concentric, as in the case of “watermelon” tourmaline, a pink core surrounded by a green rind. Or the variation may have a distinct triangular pattern as in the case of liddicoatite
Tourmaline is mined in large quantities in the United States (California and Maine) and Brazil.
Native Americans were the first to discover and used these beautiful tourmalines in their jewelry long before the gemstone industry started to mine them in the late 1870’s.
Here are some of our pieces with African Opal
