- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
Metamorphosed calcareous concretions found in lower Birrimian schists (Precambrian) of the Gold Coast are similar in appearance to "pseudodiorite" nodules from the southern Appalachians. The cores are chiefly quartz, plagioclase, garnet, clinozoisite, and hornblende; the outer portions carry these minerals and, in addition, biotite. Both the cores and the outer portions are aplitic in texture; the latter also contain numerous unoriented amphibole crystals. The history of the nodules is explained.