Increasing concern with the hazard of asbestos in schools has prompted widespread interest in the detection and identification of asbestiform minerals. Polarized light microscopy is the only method of choice for this task. Precautions for obtaining representative samples are given. Criteria for identifying and differentiating the various asbestiform materials, ground glass, mineral wool, glass wool, diatomaceous earth, micas, clays, perlite, lizardite, antigorite, other amphiboles, cellulosic fibers, and organic fibers are discussed and illustrated.