perlite - screened and partially dried perlite pellets and popped perlite - set of two 2-ounce jars
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, crushed, 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, forming a white mass of minuscule glass bubbles, changing from gray to white.
Perlite ore ranges from gray to black, with the black looking just like weathered obsidian, which it is. We have hand and student specimens of gray perlite ore in stock. The ore plus this set of two jars, makes a useful teaching set.
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