Volcanic rocks and basaltic rocks
Basalt is only one of the basic rock of its chemical composition of silica, aluminum oxide, iron oxide, calcium oxide, magnesium oxide (and a small amount of potassium oxide, sodium oxide), the mineral composition mainly by the basic Feldspar and pyroxene, secondary minerals are olivine, amphibole and biotite, etc., the rocks are dark, usually black, sometimes gray and dark purple and so on.
According to the content of SiO2 in the chemical composition, the content of SiO2 in the chemical composition (SiO2 is more than 65%), the neutral rock (SiO2 is between 52% and 65%), the basic rock (SiO2 is between 45% and 52% , Ultrabasic rocks (SiO2 less than 45%).
A volcanic rock is a magma spray surface cooling and solidification of the formation of the rock is also known as the "jet rock." Most of the faster condensing, minerals did not have time to crystallization, it is more aphase, vitreous Or microcrystalline, fine crystal, plaque structure.
