How Is a Snowflake Obsidian Formed?
Snowflake obsidian is unique because it is the only member of the obsidian family that is technically a rock, rather than glass. It is similar in composition to both rhyolite and granite, both of which also have a high silica content. The primary difference in its formation is that it has a faster cooling rate, and so contains less mineral deposits.
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Appearance
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Obsidian is found in shades of black, brown and red. Snowflake obsidian is a black obsidian that contains white or white-gray flakes. The stone is generally smooth, but has sharp edges when cut or chipped away. Snowflake obsidian is unique because, unlike other obsidians, it is not pure glass. Because it cools at a cooler temperature, it contains crystal segments that are technically rock.
Composition
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Obsidian has an almost total absence of mineral crystals and rock impurities. Specifically, obsidian is about 70 percent silica. Snowflake obsidian is a black glass that contains crystal particles. The crystal particles trapped in the glass are a type of quartz called cristobalite. These quartz crystals, if examined independently, are imperfect, with knifelike edges.
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Formation
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Obsidian is formed when molten lava erupts from a volcano and cools rapidly. Specifically, as lava moves toward the Earth's surface, the water content evaporates, causing the lava to thicken. Its thickness makes it move slower. When the cooling process is slowed, crystals begin to form in the otherwise smooth glass of the obsidian. These crystals , called spherulites, have a quartz core, and create the snowflakes in the otherwise black glass.
Location
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Obsidian forms both above and below ground. Below ground obsidian forms in volcanic vents; this is typically the highest quality obsidian. It also forms just on top of the ground surface when lava flows out of the ground and over land. Obsidian is only found in locations where there is or has been volcanic activity, and where there is a high silica content. In the United States, it occurs only along the west coast, and is found most prominently in Oregon.
Uses
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Obsidian has been shaped by man for several purposes. Historically, obsidian's edges were sharpened used to form arrowheads and cutting tools. More recently it has been incorporated into jewelry as a decorative stone, and used by metaphysical practitioners as a stone of power.
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