Earth basalt volcanic eruption stone has a shell
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%).
Basalt is just one of the basic rocks. Its chemical composition is silica, aluminum oxide, iron oxide, calcium oxide, magnesium oxide (and a small amount of potassium oxide, sodium oxide), the mineral composition is mainly composed of basic feldspar and pyroxene, secondary minerals are olives Stone, hornblende and biotite, etc., the rocks are dark, usually black, sometimes gray and dark purple and so on.
A volcanic rock is a magma sprayed surface cooling and solidification of the formation of the rock is also known as the "ejector rock". Mostly condensed faster, minerals did not have time to crystallization, it is mostly submerged, vitreous or microcrystalline, fine grain, plaque structure.
Most of the stones on earth are not shells. Because the stones are volcanic through countless, countless years of wind and sun, countless, countless years of thermal expansion and contraction formed, and the shell only in the volcanic surface, resulting in volcanic rocks are mostly melting shell.
