State by State
- Specimen Number
Weathered boulder of pervasively altered granite with an rusted rim (cortex). Identified by the Missouri Survey as the Slabtown Granite, described by the USGS, a "fine-grained granite, usually porphyritic, mottled pink and green (mafic minerals)... Weathers to dull buff to brown, blocky, tabular cobbles." This description matches our sample.
Igneous. Plutonic. Granitic. Granite.
- Location & Occurrence
Slabtown Granite Formation occurs in the St. Francois mountains in the southeastern part of the state. From the map, the southeastern part of the state is most highly deformed and faulted.
- Geological Age
Precambrian. Proterozoic, with a Rb-Sr age of ~1300-1400 Ma.
Ancient rock from an otherwise inconspicuous orogen.