![]() This is because glass is amorphous, not crystalline in structure. A type of igneous rock, called extrusive igneous rock, obsidian is extruded from the Earth as lava which when rapidly cooled forms a natural glass.Īs a volcanic glass, obsidian is mineral-like, or mineraloid, but is not a true mineral. Obsidian, or lapis obsidianus, is essentially dark glass. Obsidian is an ancient rock that was discovered in Ethiopia by a Roman explorer named Obsidius. Numerous surgeons also use obsidian blades as scalpel blades.Obsidian is a natural glass formed by the meeting of lava from an erupting volcano with cold air or water, imbuing obsidian with all four elements: earth, fire, water, and air. An obsidian blade is a glass knife built using the naturally occurring material. It can be used to make cutting edges which are sharper and thinner than surgical steel. Currently, they used for ornamental purposes, and as a popular stone, it’s often cut into cabochons and beads. It was used to make scrapers, spear points, arrowheads, and knives among other tools and weapons. Obsidians were broken and polished to create the early mirrors. The Stone Age cultures valued obsidians since they could be fractured to make arrowheads or sharp blades. The first evidence of human beings using obsidian was found in Kariandusi and numerous other Acheulian age sites that date back to 700,000 BCE. Tektites were previously believed to be obsidians formed by the eruption of lunar eruptions. Intrusive creation of obsidians occurs when the lava cools beside the dyke’s edge. It is also formed when lava cools once it comes into contact with air or water. Obsidians forms when the felsic lava cools at the edges of a volcanic dome or felsic lava flow. They can also be located in the eastern US states of North Carolina, Pennsylvania, and Virginia. Obsidian flows that can be hiked are in the Calderas of Lake Medicine Volcano and Newberry Volcano. They can be found in the United States, Turkey, Scotland, New Zealand, Mexico, Japan, Kenya, El Salvador, Canada, Australia, Armenia, and Argentina. Older obsidians are rare since they are altered or destroyed by heat or weathering. Obsidians are found in places that have experienced recent volcanic activities. ![]() The presence of water on the earth’s surface hastens the break down process of the obsidian. Obsidians can break down into some fine-grained mineral crystals with time since it is metastable. They are made up of over 70% silicon dioxide. The transition elements can give them brown, green or tan color. Obsidians are black although their color varies depending on the presence of inclusions or trace elements. It is not a true mineral since it’s not a crystalline solid therefore it’s classified as a mineraloid. Obsidians were used to produce piercing and cutting tools during the stone ages. ![]() The curved smooth fractures are formed due to the lack of mineral crystal in the obsidian. Obsidians are brittle and hard volcanic glasses which break with distinctive conchoidal fractures. They are found on the obsidian flows where the high quantities of silica induce a high degree of polymerization and viscosity of the lava that inhibits crystal growth. Obsidians are volcanic glasses referred to as mineraloids. They are formed when felsic lava cools quickly with minimum to no crystal growth. Obsidians are naturally occurring amorphous products of fast cooling magma.
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