Trondhjemite
Videos
Trondhjemites are leucotonalites, a variety of leucocratic tonalite in which the modal mineralogy mostly consists of plagioclase in the form of albite to andesine, >20% quartz, and <10% alkali feldspa
Tonalite-trondhjemite-granodiorite migmatite (left) and trondhjemitic gneiss (right) from northern China
Color index (geology)
Videos
Color index, as a geological term, is a measure of the ratio between generally dark mafic minerals and generally light felsic minerals in an igneous rock. The color index of an igneous rock is the vol
Trondhjemite
…Trondhjemites are leucotonalites, a variety of leucocratic tonalite in which the modal mineralogy mostly consists of plagioclase in the form of albite to andesine, >20% quartz, and <10% alkali feldspar…
Gneiss, displaying characteristic darker (melanocratic) and lighter (leucocratic) bands