Fused Glass October Birthstones – Opal
Opal is one of October’s birthstones and also commemorates a 14th wedding anniversary. The name opal derives from the Greek Opallos, meaning “to see a change (of color).” Opals formed at low temperatures from silica-bearing waters and they can occur in fissures and cavities of any rock type, usually sedimentary rock. Silica collects into spheres of uniform distribution and size, they packed together efficiently thus creates precious opal. The color of the gem is due to fine-grained impurities. Like agates, every opal is unique. Opal is a delicate and soft stone, rating a 5.5 to 6.5 on the hardness scale. Opals are classified according to their body color and the play of color they have.
• White opals are the most common types, with a body color of white, cream, or yellow.
• Fire opals are translucent or transparent, with no color play. A honey-yellow to hyacinth-red and shows intense orange and red fire-like reflections. The only Opal variety that can be faceted.
• Water opals, this variety has body color of transparent to translucent. It shows little or no play of color and hence is low in value.
• Black opals are the most precious type of opals. Top quality black opals can be more expensive and valuable than diamonds. * Black opals should not be completely black otherwise, it would be worthless, it should display a myriad of rainbow colors, the more colorful the better.
• Crystal opals are also transparent, but they do have the play of color.
• *Boulder opals have a layer of stone from mining left on opal that occur in a thin layer. Boulder opals can command prices second only to black opals.
Composite Opal – Opal Doublet and Opal Triplet
Opals used in jewelry are usually one piece of solid opal. However, some opals are very thin layers (i.e., very fragile), these opals are sometimes glued to a base of obsidian, potch, basalt, etc. The combination is called “opal doublets”. In order to protect the opal layer of the doublet, a transparent top (i.e., quartz) is sometimes placed over it. Now the three piece stone is called “opal triplet”.
It is believed opals have special properties:
• Be able to make the owner happy, normally it shines if the wearer is happy and stop shining if the wearer is moody.
• Gives the wearer little foresight and memory power
How to Care for Opal
The fire, or color, in opals is made by the cracks in it, thus its beauty is also its weaknesses (the cracks are not visible to the naked eye). Treat opals with care to prevent any scratches or blows. Opals should never be kept in oil or any other chemicals. Opals contain 5-20% water, which dries out over the years, causing them to become brittle and lose their hardness. If opals get too dry, they tend to crack. This phenomenon is called “Crazing,” and it wipes out the value of the stone. Avoid leaving opals near anything potentially drying. To keep opals from drying, it may be helpful to immerse it in water for several hours from time to time. The exception is if the opal is a doublet or triplet opal, which can be damaged by prolonged exposure to water which can cause the glue to deteriorate and separate the layers.
For the fused glass birthstone version of Octobers’ “Opal” I used various shades of glass & dichroic. I love opal which is one of the reasons I was drawn to fused glass. So many of my pendants and rings have been mistaken for opals.
Keeping my kiln warm