A Geoscience Digital Image Library

TitleThin section of tonalite (quartz diorite)
DescriptionThis is a plain polarized thin section of tonalite (quartz diorite). The sodic plagioclase and hornblende are subhedral. The other essential species, quartz and biotite, are anhedral. Some of the basal sections of hornblende show twinning. Biotite is partly chlortizied. Coarse anhedral epidote and orthoclase, magnetite, apatite, and allanite are accessories. Plagioclase is slightly zoned; quartz is undulatory in extinction.
ChronostratigraphyUpper Cretaceous
Geologic provinceBonsall Tonalite
LocationUSA ▹ California ▹ San Diego. Near San Diego.
PhotographerDarla Sondrol. 2002-04-09.
CollectionWard’s Collection of Classic North American Rocks #24.
Key wordsBonsall, tonalite, quartz diorite, California, thin section
Tech details672 KB. Thin section. Nikon FDX-35.
GeoDIL number2627