To identify which type of insulation exists in your home, it is important to learn the differences between rock wool and vermiculite.
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Observe the texture of the insulation. Vermiculite insulation is loosely packed and granular in appearance, often resembling small pebbles. The size of the pieces may vary from 1/8 inch in diameter to 1/2 inch. Rock wool is made up of soft fibers, rather than loose particles, and has a cottony appearance.
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Observe the color of the insulation. Vermiculite insulation is made up of gray or brown particles that may be sprinkled with bits of reflective gold or silver mica. Rock wool can be either white, off-white or brownish white.
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Slip your protective gloves onto your hands. With your gloved hands, feel the texture of the insulation. Vermiculite insulation feels granular between your fingers, almost like small pieces of gravel. In contrast, rock wool feels like dense wool.