Green obsidian orb vs glass free#

Obsidian typically forms near the end of a volcanic cycle and is often associated with domes of volcanic rock, such as the hills of Glass Buttes, Oregon. In North America, obsidian is found only in localized areas of the West, where the processes of plate tectonics have created geologic conditions favorable to volcanism and the formation of obsidian. Obsidian-bearing volcanoes are typically located in or near areas of crustal instability or mountain building. Obsidian occurs only where geologic processes create volcanoes and where the chemical composition of the magma is rich in silica.

In comparison, quartz (crystallized silicon dioxide) has a hardness of 7.0. Obsidian is relatively soft with a typical hardness of 5 to 5.5 on the mineral hardness scale. Because obsidian is not comprised of mineral crystals, technically obsidian is not a true 'rock.' It is really a congealed liquid with minor amounts of microscopic mineral crystals and rock impurities. It is chemically similar to granite and rhyolite, which also were originally molten. Obsidian consists of about 70 percent or more non-crystallized silica (silicon dioxide). This had obvious advantages for our Stone Age ancestors, who used obsidian extensively for tool making. The intersections of conchoidal fracture surfaces can be sharper than a razor. This smooth, curved type of fracture surface occurs because of the near-absence of mineral crystals in the glass. Like all glass and some other types of naturally occurring rocks, obsidian breaks with a characteristic 'conchoidal' fracture. These relatively large mineral crystals (easily visible to the naked eye) give granite a rough fracture surface. Granite is composed entirely of intergrown crystals of quartz, feldspar, mica and other minerals.

Green obsidian orb vs glass free#

Crystal faces form only where there is enough open space in the rock mass to allow the natural geometric forms of the crystals to develop as free faces. When crystallization occurs, the atoms that comprise a mineral become arranged in regular, geometric patterns that are unique to the specific mineral. All rocks consist of mixtures of various crystalline minerals.

When I say 'crystals,' don't visualize those beautiful pointed prisms of quartz found in geodes. This volcanic glass has an almost total absence of sizable mineral crystals within the glass matrix. Obsidian is natural glass that was originally molten magma associated with a volcano. My goal in this article is to increase your awareness of some of the more fascinating aspects of this incredible stone. The ancient volcanic hills called Glass Buttes hold a dazzling variety of gem-quality obsidian, including: mahogany, red, flame, midnight lace, jet black, pumpkin, brown, rainbow, gold sheen, silver sheen, green, lizard skin, snowflake and more. But until a few years ago when I made my first obsidian collecting trip to Glass Buttes, Oregon, I thought obsidian was pretty much just black glass.

Sharp and shiny, obsidian is so different from other rocks. Ever since I had my first rock collection as a child, I've loved obsidian.