Glass Butte is the largest deposits of the high-quality obsidian in the world.įor rock-hounding purposes, the area is mostly known for its obsidian. Glass Buttes and adjacent hills are located off of the milepost 77 of US route 20 highway and the area is characterized by volcanic mountains and rolling hills covered by sagebrush.
SNOWFLAKE OBSIDIAN BEDS UTAH FREE
Characterized by volcanic mountains and rolling hills covered by sagebrush, the 6,000-acre area has been designed a Free Public Use Area. A favorite destination for rock hounds, those two sites are located approximately half-a-mile away from each other. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight.Two prominent peaks Glass Butte and Little Glass Butte in the Oregon high desert, just 57 miles west of Burns and 78 miles east of Bend, are known for its wide diversity of obsidian. Because volcanic bombs cool after they leave the volcano, they do not have grains making them extrusive igneous rocks. They cool into solid fragments before they reach the ground.
A volcanic bomb is a mass of molten rock larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption.Best Field Indicators are color, fracture, flow bubbles, softness, association with other volcanic rocks and lack of crystal faces.Notable Occurrences include Italy Mexico Scotland Arizona, Colorado, Texas, Utah and Idaho, USA, as well as the Cascade Volcanic Mountain range and its associated lava beds, which stretches from Northern California into Washington state.Other Characteristics: Generally lacks open voids or large bubbles like other volcanic rocks.Specific Gravity is approximately 2.6 (average).Hardness is 5 - 5.5 (much softer than quartz).Habits include compact nodules or as massive layers between other volcanic rocks.
Crystal System does not apply because obsidian is amorphous.Transparency: Obsidian is translucent in any stone of appreciable size.Sometimes with white inclusions (Snowflake Obsidian). Color is dark green to dark brown and black, also can show sheens of gold or green, yellow, blue and/or purple coloration.Obsidian has been used by ancient people as a cutting tool, for weapons, and for ceremonial purposes and is sometimes found by archaeologists in excavations. These bubbles can produce interesting effects such as a golden sheen ( sheen obsidian) or an iridescent, rainbow-like sheen ( rainbow obsidian). It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern ( snowflake obsidian). Iron and magnesium typically give the obsidian a dark brown to black color. Pure obsidian is usually dark in appearance, though the color varies depending on the presence of impurities. Obsidian having low water content when newly formed, typically less than 1% water by weight, becomes progressively hydrated when exposed to groundwater, forming perlite. This breakdown of obsidian is accelerated by the presence of water. Because obsidian is metastable at the Earth's surface (over time the glass becomes fine-grained mineral crystals), no obsidian has been found that is older than Cretaceous age. Crystalline rocks with obsidian's composition include granite and rhyolite (parent material). Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% or more. Though obsidian is usually dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic. It is sometimes classified as a mineraloid. Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline in addition, its composition is too complex to comprise a single mineral. SiO2 Mostly silicon dioxide with large amounts of impurities. When obsidian is ejected from a volcano and cools rapidly in the air and falls to earth it is known as an obsidian bomb. Iron and magnesium give the obsidian a dark green to black color. This process produces a glassy texture in the resulting rock. Often the lava pours into a lake or ocean and is cooled quickly. Obsidian is the result of volcanic lava coming in contact with water. Obsidian is actually glass and not a mixture of minerals. Obsidian is igneous rocks formed as a result of magma, the parent material, cooling rapidly above ground, which is the parent material.
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