Specimen: 2015-001
This specimen is a sandstone. Detrital grains constitute 65 to 75 percent of slide area, void space is approximately 10 to 15 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. This estimates suggest the sandstone is composed of an immature to submature parent material. Compaction has mostly obscured the shape of original grains, but rounded to subrounded is most likely. Of the detrital grains, quartz comprises about 85 percent of grains. Feldspars constitute most of the remaining component with various species of mica and fine grained lithic fragments contributing only small amounts. Based on these estimates this sandstone is classified as a feldspathic greywacke (this assumes much of the void space was originally fine-grained matrix). The constituent grains are poorly sorted. Maximum grain size is .8 mm and minimum is .02 mm. The modal size is around .3 mm. Feldspars show a variety of weathering states, with some grains predominantly transformed to alteration products such as sericite. Biotite is also significantly altered with kaolinite formation causing significant foliation. The matrix material is predominantly composed of a mix of carbonate, clay, and secondary mica species too microscopic to definitively identify. No visible macrostructure, such as bedding is visible in thin section. The hand sample also lacks apparent structure.
MP 9/5/2015