Obsidian scalpel scar3/18/2023 It is then called "sheen obsidian" or "rainbow obsidian," respectively. As a result, the rock may acquire an interesting appearance, such as a golden sheen or rainbow sheen. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produces a blotchy or snowflake pattern, and the rock is called "snowflake obsidian." Alternatively, the rock may contain patterns of gas bubbles, aligned along layers created as the molten rock flowed before solidifying. The presence of iron and magnesium typically gives the material a dark green or brown or black color. Pure obsidian is usually dark in appearance, but the color varies depending on the presence of impurities. Pig carved in snowflake obsidian, 10 centimeters (4 inches) long Quartz, however, is crystalline, and several of its properties therefore differ from those of obsidian. In some ways, obsidian resembles quartz because of their similar chemical makeup. Like any other type of glass and some other types of naturally occurring rocks, it breaks with a characteristic conchoidal fracture. Its relative density is approximately 2.6. It is relatively soft, with a typical hardness of 5 to 5.5 on the Mohs scale. Its composition is very similar to that of granite and rhyolite. Obsidian consists mainly of silicon dioxide (SiO 2), usually 70 percent or more. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, but few scientists currently endorse this hypothesis.Īmong other places, Yellowstone National Park has a mountainside containing large quantities of obsidian, located between Mammoth Hot Springs and the Norris Geyser Basin. Consequently, no obsidian has been found that is older than the Cretaceous age. The breakdown of obsidian is accelerated by the presence of water. This glassy rock is metastable-over time, it becomes fine-grained, mineral crystals. This rock can be classified as an "extrusive" igneous rock-that is, igneous rock formed by the cooling of lava on the Earth's surface. It is commonly found in areas where the cooling of lava was rapid-such as at the margins of the lava flows and in places where the lava entered a lake or sea. Obsidian is produced from volcanoes when felsic lava cools and freezes without sufficient time for crystal growth. In addition, the rock continues to be used for ornamental purposes and as a gemstone. ![]() ![]() It is currently used for manufacturing surgical scalpel blades, as the blade edges can be made to approach molecular thinness. People of early cultures used obsidian to produce weapons, tools, mirrors, and decorative objects.
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