A Geoscience Digital Image Library

TitleRhyolite porphyry, St. Francois Mountains, Missouri
DescriptionThe visible whitish crystals are quartz phenocrysts up to 1-2 mm in size, but most of this sample is so fine grained that minerals cannot be identified. In thin section, identification is only slightly easier, but fine grained quartz and K-feldspar can be seen. This sample 11 cm across.
LocationUSA ▹ Missouri. St. Francois Mountains.
PhotographerMike Davis. 2001-04-26.
CollectionWard’s University Rock Collection #108.
Key wordsrhyolite porphyry, Missouri
Tech details571 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera, 60mm AF Nikon micro lens.
GeoDIL number416