Specimen: 2015-002
This specimen is a sandstone. Detrital grains constitute 70 to 80 percent of slide area, void space is approximately 10 to 20 percent, and the remaining area is occupied by fine grained matrix. Much of the void space may be the result of recent weathering, formally filled by matrix. These estimates suggest the sandstone is composed of an immature to submature parent material. Compaction has obscured the shape of original grains, but rounded to sub-rounded most likely predominated. Of the detrital grains, quartz comprises about 95 percent of grains. The remaining component includes feldspars, muscovite, mafic minerals (pyroxene, amphibole, opaques), and lithic fragments. Based on these estimates this sandstone is classified as a quartzwacke (this assumes much of the void space was originally fine-grained matrix). The constituent grains are well sorted. Maximum grain size is .4 mm and minimum is .08 mm. The modal size is around .2 mm. The matrix material is predominantly composed of mica and platy mineral species too microscopic to definitively identify but presenting perceptible book habits. A few inter-grain areas are filled with opaque minerals as opposed to low birefringent platy minerals. No visible macrostructure, such as bedding, is visible in thin section. The hand sample also lacks apparent structure.
MP 9/5/2015