A simple, low cost adaptor for converting transmitted light microscopes to polarized light microscopes was described. The adaptor was intended to assist in examining and identifying asbestos (1332214) fibers. The adaptor consisted of a polarizer, an analyzer, a retardation plate, a stage rotation device, and central and annular stops for dispersion sampling. The adaptor was designed to fit conveniently into a mechanical stage device and to be used with 10X objectives. A wide variety of microscopes was converted to polarized light microscopes which were found to be adequate for identifying asbestos in bulk insulation samples. Design specifications for the various components of the adaptor were provided. The authors note that the adaptor can be made easily and at low cost from readily available materials. In addition to asbestos, the adaptor can be used to identify other fibrous materials such as glass fibers, mineral wool, or cellulose, and nonfibrous materials such as silica, calcite, or olivine. The microscopes are also recommended for training industrial hygiene personnel and in field and screening identification applications.