Definitions for "Ultrabasic"
An igneous rock that consists of ferromagnesian minerals and possesses no free quartz, and with less than 45% silica.
Describing an igneous rock containing magnesium and iron with a very low percentage of silica, less than 45%.
Igneous rock containing less than 45 per cent silica.
Keywords:  ultramafic, see
see Ultramafic