However, when it cools down afterwards, it returns to its translucent or opaque state and becomes whitish again.Ĭristobalite occurs in igneous rocks located in areas of volcanicĪctivity, often lining gas bubbles in the host rock.Ĭristobalite is used in scientific study. When heated to 350✯ (180✬), Cristobalite becomes clear and transparent. Crystals are occasionally cubic.ġ) Crystals exhibit a strong double refraction. It also occurs massive, platy, crusty, and stalactitic. Cristobalite is much more common in globular groups and as crusty rounded balls. The octahedral crystals may be twinned with Spinel twinning. White, light gray, light yellow, light brown, blue-grayĬristobalite is a always a pseudomorph after Beta Cristobalite, which crystallizes in the isometric system, and thus Cristobalite occurs in isometric shaped crystals.Ĭlick here for a detailed explanation on the crystal structure of Cristobalite and other forms of silica.Ĭrystals are usually in microscopic grains, and small octahedral crystals can be made out under magnification. Snowflake obsidian, a popular form of obsidian with white snowflake-like formations on it, is in fact obsidian with small white inclusions of Cristobalite, where the white microscopic crystals form a pattern giving it a snowflake-like effect. It usually forms in vesicles and gas pockets with the obsidian. Cristobalite is found in volcanic sources almost always associated with the natural glass rock obsidian. It is composed of the same elements as Quartz but has a different crystal structure, making it a separate mineral. Silicon Dioxide + Magnesium Oxide and/or Iron Oxideīlack, bluish, brown, red, mahogany, golden, rainbow the colors are largely due to refraction by microscopic bubbles and/or microscopic mineral inclusions.Cristobalite is an odd form of silica. The material offered for sale is, in fact, a man-made glass produced in places such as Indonesia and China. Please note: “Transparent blue or green Obsidian”Ī lot of gem-quality water-clear brightly colored “O bsidian” has been offered for sale on the internet with a variety of sources listed. Where ever this material comes from or however it was formed, it is a stunning gem of the finest Tsavorite green color. Some say it is a natural volcanic glass, some argue that it is man-made glass, others claim it is of meteoric origin similar to Moldavite. It is reported to be found in alluvial deposits and in a river bed at the base of Mt. One source says the Tanzanian natives call it Obsidianite. This mysterious gem has been called many names including Green Obsidian, African Moldavite, Tanzanian Tektite, Green Volcanic Glass and green man-made glass. Apache Tears are usually translucent to transparent and medium brown in color. The wives and families of the warriors cried when they heard of the tragedy and their tears turned to stone upon hitting the ground. Facing defeat, the outnumbered Apache warriors rode their horses off the mountain to their deaths rather than be killed by the soldiers. The legend is that about 75 Apache warriors and the US Cavalry fought on a mountain overlooking what is now Superior, Arizona in the 1870s. These are often called Cosmic Obsidian.Īnother type of Obsidian is called “Apache Tears” because of a legend of the Apache tribe. There are also translucent Obsidian gems with white inclusions of Cristobalite. Rainbow Obsidian has an iridescent, rainbow-like sheen. Mahogany Obsidian has brownish-red patches or swirls of black Obsidian while Snowflake Obsidian has greyish white patches of black Obsidian. The most common are opaque cabochons of black, Mahogany, Snowflake or Rainbow Obsidian. There are several types of Obsidian typically offered as gems. Most Obsidian is typically opaque black and not desirable for faceting. It is sometimes classified instead as a mineraloid. Otherwise, it is very similar in composition to granite and rhyolite. Obsidian consists mainly of silicon dioxide and is mineral-like, but not a true mineral because it has no crystal structure and therefore is amorphous. It is produced from volcanoes when certain types of lava cool rapidly by flowing into a body of water. Obsidian, also known as volcanic glass, is a rock rather than a mineral that is a mixture of cryptocrystalline grains of silica minerals in a glass-like suspension.
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