Obsidian (Sample #7)
Rock Type: Igneous (volcanic glass)
Composition: It has a similar composition as granite with 70% silicon dioxide, felsic
Particle size: Fine cannot see with naked eye, volcanic glass
Hardness: 5.5 however it can easily chip and shatter like glass.
Hardness: 5.5 however it can easily chip and shatter like glass.
Luster: Vitreous
Environment: Obsidian forms when molten lava cools so rapidly that a crystalline structure is unable to form.
Distinguishing Characteristics: It has a smooth uniform texture with a glassy appearance and breaks with a conical fracture. It is often black and glassy but can have white crystals such as snowflake obsidian. Obsidian can break and form very sharp edges making it suitable for knives and cutting points.
Uses: Obsidian has been used throughout history as a cutting to, made into knives, spear points, arrowheads. Today obsidian blades are being used in modern surgery since they are thinner and sharper then surgical steel and perform better in delicate operations. Obsidian is also used in jewelry.
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