perlite - teaching hand specimen of gray perlite ore - an amorphous hydrated glass
Perlite is a hydrated form of obsidian. When a mass of obsidian picks up water, it devitrifies and becomes amorphous perlite. The unhydrated core of the obsidian mass may weather out as an obsidian spherule called an Apache Tear.
Perlite can also form by the sudden cooling and solidification of rhyolitic volcanic ash, which traps water into its mass.
Perlite is mined, partly dried in a rotary kiln and screened to various sizes depending on its final application. To make the white perlite "rice krispies" found in garden supplies and nurseries, the partly dried perlite is heated to 1,600˚F. The internal water flashes to steam and the perlite pops, just like popcorn, and changes from gray to white.
This perlite was collected from a deposit in the Big Pine volcanic field in Inyo County, California.
Perlite ore ranges from gray to black, with the black looking just like weathered obsidian, which it is. We also stock the partly dried and screened perlite in the "before popping" stage as well as the final product. The series, from ore partly dried to final product makes a useful teaching set. These forms are available in a set of two 2-ounce jars.
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