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Opal is the October Birthstone by Harry W. Short, Engineering Geologist Opal, the October birthstone, was highly prized by the Greeks and Romans. One ancient in about 500 B.C. said, "The delicate color and tenderness of opal reminds me of a loving and beautiful child." Pliny prized the opal so highly, he ranked it next to emeralds. He described it in such glowing terms the modern writers still quote his description. An extremely beautiful gemstone, opal is cherished because of its mystic display of colors. Almost every color in the spectrum, from colorless to shaded with tints of red, yellow, green, blue, black, or white, are found in opal. It occurs in a wide variety of shapes and forms, and is often transparent or opaque. The luster of the numerous varieties of opal may be vitreous, subvitreous, resinous, pearly, or dull. Opal is made of silica similar to quartz; however, there is a big difference between the two. Opal is not crystallized like quartz, and may contain up to 15% water. In the earth, opal was likely a silica gel because of the great pressures and temper- atures deep underground. Superheated waters dissolved silica from existing rocks and transported it upward to the earth’s crust. As the temperature and pressure dropped near the earth's surface, the silica filled joints, veins, and fissures with opal. You can find opal in sedimentary, igneous, and metamorphic rocks. It is the chief constituent in the skeletons of diatoms and petrified wood. Opal is most commonly found in regions of mountain building, lava flows, ash beds, and sedimentary rocks in contact with igneous rocks. Many impurities found in opal, such as iron oxide, alumina, lime, magnesia, and alkalies account for the several different varieties of opal. Opal held its coveted prestige with its owners until Sir Walter Scott wrote a book in 1829, chastising the stone, saying it brought bad luck to holders of the gemstone. Another bit of fiction further perpetrated the decline of opal jewelry. It was said an enchanted princess wore a beautiful opal in her hair, and it glowed in response to her mood. One day, a few drops of water accidentally touched her opal and it faded immediately. The princess died and all that remained of her body the next day were ashes on the spot where she fell. Harry In memory of Harry Short. His articles will continue posthumously. Contact: michele@worldwidedrillingresource.com )' ) % ) ' # *# $ ' : &4)1*4 *18*4 : : &4)1*4 *18*4 : : &4)1*4 *18*4 : : &4)1*4 *18*4 % ( ) ' ) '%# : &4)1*4 *18*4 : : &4)1*4 *18*4 : : &4)1*4 *18*4 : &4)1*4 *18*4 : &4)1*4 *18*4 ' $ + *#&( $ )% ! &4)1*4 *18*4: # #4 3 *: ! ! &4)1*4 *18*4 : # #4 3 *: ! ! &4)1*4 *18*4: 24 : 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : 4 4 8* 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : # #4 3 *:>> ! ! &4)1*4 *18*4 : #4 3 *:>> > ! ! ;)4&7 ( 4276 703 ? ;)4&7 ( 4276 703 ? ;)4&7 ( 4276 703 ? '%*) *#& * ") * *#&( : &52 73 *: ! ! : 9* 73 *: ! ! &4)1*4 *18*4 : #4 3 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &4)1*4 *18*4 : 73 *: ! ! &52 : 73 *: ! ! '#()'%$ $ % $ "% 6, "64**6 = 2(&,216&5 $" < 2745 &;5 & %**. = &: %&665 $" &1&)& 62 21)&; 4 )&; "** 274 %*' &+* 999 &4056421+0&(, 1* (20 0& ))4*55 &0( &4056421+0&(, 1* (20 18 OCTOBER 2016 WorldWide Drilling Resource ®