Obsidian And Granite

Obsidian consists mainly of sio 2 silicon dioxide usually 70 or more.

Obsidian and granite. Rarely volcanic glasses are found with a composition similar to basalt and gabbro. Because obsidian is metastable at the earth s surface over time the glass becomes fine grained mineral crystals no obsidian has been found that is older than cretaceous age. Obsidian consists mainly of sio 2 silicon dioxide usually 70 by weight or more. Granite is of intrusive origin which means the magma.

Obsidian igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth 1 2 history. Granite is a very hard granular crystalline igneous rock which consists mainly of quartz mica and feldspar and is often used as building stone obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. We have seen in the earlier section that obsidian is an extrusive rock type and formation used to takes place on the surface of the earth when magma or lava coming out due to volcanic phenomena and rapid cooling takes place.

Obsidian is not a genuine mineral or rock it is a natural glass that contains microscopic mineral crystals. Granite is a light colored igneous rock with grains large enough to be visible with the unaided eye. Obsidian and granite are both igneous rocks. Granite is composed entirely of intergrown crystals of quartz feldspar mica and other minerals.

Obsidian is of extrusive origin which means the magma cooled quickly and has a glassy texture. Formation of obsidian rocks in nature. Crystalline rocks with obsidian s composition include granite and rhyolite. Like all glass and some other types of naturally occurring rocks obsidian breaks with a characteristic conchoidal fracture.

Obsidian and granite are igneous rocks so called because they were formed from the molten magma of volcanoes. Obsidian is extremely rich in silica about 65 to 80 percent is low in water and has a chemical composition similar to rhyolite. These glassy rocks are named tachylyte. It forms from the slow crystallization of magma below earth s surface.

Granite is composed mainly of quartz and feldspar with minor amounts of mica amphiboles and other minerals this mineral composition usually gives granite a red pink gray or white color with dark mineral. Beyond that their similarities end. Granites and rhyolites can form from the same magma as obsidian and are often geographically associated with the obsidian. These relatively large mineral crystals easily visible to the naked eye give granite a rough fracture surface.

Most obsidians have a composition similar to rhyolite and granite.