More than 100 mineral specimens of 18 types were collected and classified to provide reference materials for developing analytical methods for monitoring workplace contaminants. Mineral specimens were comprised of those frequently found in industry. The samples were pure and similar in particle size to commonly encountered industrial dusts. Reference standards included five asbestos (1332214) minerals in fibrous and nonfibrous varieties, three silica polymorphs, (7631869) several minerals used as internal standards in current methods for analyzing silica polymorphs, and talc (14807966). Several specimens of each mineral were subjected to multilevel screening to select appropriate specimens for processing as final mineral standards. Screening included macroscopic evaluation, polarized light microscopy (PLM), X-ray diffraction (X- RD) and differential thermal analysis (DTA). When the optimum grinding and beneficiation procedure for each mineral sample had been determined, the best of each type was purified and ground. Final reference materials were again subjected to PLM, X-RD, and DTA. Particle size distributions of the final products were monitored.