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Opal:
Tectosilicates Hydrous silica, often with some iron and aluminum SiO2 . nH2O; amount of water varies up to 10 percent AKA: Black opal, Fire opal, White opal, Wood Opal |
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System: None; usually massive, botryoidal, reniform, stalactitic, earthy. Appearance: White, yellow, red, pink, brown, green, gray, blue, colorless; frequently shows rich internal play of colors (opalescence) in precious opal or fire opal; pearly; streak white. <Physical Properties: Hardness: (5.5 - 6.5); Specific gravity: (2.0 - 2.2). Cleavage: none, usually massive, botryoidal, reniform, stalactitic, earthy; fracture, conchoidal, conspicuous when compact; transparent to translucent; fluorescent. Similar species: Dense opal resembles quartz, but it is softer and has a lustrous conchoidal fracture. Occurrence: Opal is a low-temperature mineral and usually develops in a wide variety of rocks as cavity and fracture fillings. It frequently develops as amygdules in basalt and rhyolite of volcanic rock and replaces the cells in wood and the shells of clams. Common opal is widespread and can be readily obtained at many places, but localities for precious opal are rare and seem to be localized in W United States and Mexico. Magnificent examples of opalized wood can be found in Idaho, Nevada, Oregon, Utah, and Washington, and a lively green fluorescing opal (hyalite) occurs in New England and North Carolina and in cavities in basalt near Klamath Falls, Oregon. Beautiful precious opal, as a replacement in wood, has been obtained in Virgin Valley, Humboldt Co., Nevada. Excellent fire and precious opal occur in lava flows in N Mexico, and excellent material has been mined in Queretaro and Jalisco states, Mexico. Miscellaneous: Black, dark blue, dark green opal with dark gray body color and fine play of colors is called black opal; opal with white or light body color and fine play of color is called white opal; and transparent to translucent opal with body color ranging from orange-yellow to red and play of colors is called fire opal. Play of colors depends upon interference of light and is not dependent upon body color. Black opal is the most highly prized, and fire opal is the most valued of the orange and red varieties. Most opal is fashioned into cabochons, but some fire opals are faceted. Nevada, Australia, and Honduras are sources for black opal; Australia and Czechoslovakia for white opal; Mexico and SW United States for fire opal. Very fragile, partly because when exposed to air it loses water and becomes filled with tiny conchoidal fractures (crazing). Birthstone for October. The name is from the Sanskrit upala, meaning "precious stone." Conventional Wisdom: Contains water, correlating with our emotions. Clarifies by amplifying and mirroring feelings, buried emotions and desires (including love and passion). Brings less inhibition and more spontaneity. Useful for visualization, imagination, dreams and healing. Easily absorbs, stores emotions and thoughts. Some opals can cancel or negate other gems (backfires if not used for good of all). May change color with high energy/intensity people. White: Balances the left and right sides of the brain brain. Black or Dark blue: One of the most potent opals. Potent grounding stone and concurrently stimulates activity. Fire Opals: May stimulate passion, temper, energy. Belongs to the Astrological Signs of Cancer, Libra, Pisces and Scorpio. |