This collection includes 4,525 rock thin sections archived by the DMME Virginia Division of Geology and Mineral Resources. The thin sections represent a wide range of rock types in Virginia and are available for petrographic studies. Many, but not all of these thin sections are associated with rock specimens inventoried in the Rock Repository, identified by the tag "R-#####". Other thin sections represent rock specimens from earlier studies for which documentation may exist, yet the original rock sample may not be available. The location coordinates for the thin sections are approximate, given by the 7.5-minute quadrangle centroid. Work continues on this collection to better document missing information.