Definition of "perlite" [per•lite]

• A natural volcanic glass similar to obsidian but having distinctive concentric cracks and a relatively high water content. In a fluffy heat-expanded form perlite is used as a lightweight aggregate, in fire-resistant insulation, and in soil for potted plants. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The name perlite (also spelled pearlite) comes from the French word perle which means pearl, in reference to the “pearly” luster of classic perlite."
• "The name perlite (also spelled pearlite) comes from the French word perle which means pearl, in reference to the "pearly" luster of classic perlite."
• "A: Most potting soil or seed-starting media that you purchase in a garden center is pasteurized and contains inert material, such as vermiculite or perlite, which is sterile."