DRI has acquired the latest technology in X-ray diffractometry (XRD). This is providing essential mineralogical information in support of on-going and new proposed research projects as well as complementing the capabilities of existing facilities at DRI. Despite their abundance and likely environmental and health impacts, mineralogical properties of dusts are often disregarded in speciation studies, and only the chemical compositions of the aerosols are being routinely measured. The extent to which variations in mineralogy affect dust radiative impact is poorly quantified. XRD provides mineralogical information required to assess aerosol refractive indices and other optical properties. Recent advances in XRD instrumentation, however, hold great potential for determining source areas of dust and assessment of dust properties, including toxicity and degrading visibility. DRI is developing procedures whereby aerosol samples are collected on filters and quantitatively analyzed for their mineralogical content by XRD.