The chemical composition of basalt and gabbro similar, SiO2 content varied from between 45% ~ 52%, K2O + Na2O content than intrusive rocks slightly, CaO, Fe2O3 + FeO, MgO content is slightly lower than the intrusive rocks. Mineral composition is mainly composed of mafic composition of feldspar and pyroxene, secondary minerals are olivine, amphibole and biotite, rocks are dark, usually black, sometimes grayish green and dark purple. It was patchy structure. Stomatal structure and almond universal structure.
Basalt bulk density of 2.8 ~ 3.3g / cm3, dense by compressing great strength, up to 300MPa, and sometimes higher, the strength decreased in the presence of vitreous and pores. Basalt durability is very high, joints and more possessed brittleness, thus easily mined large pieces of stone, as pores and almonds common structure, although widespread basalt on the surface, but can be used for facing stones much.
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