Basalt Granite And Obsidian Rock

Properties of rock is another aspect for basalt vs obsidian.

Basalt granite and obsidian rock. Basalt is an extrusive or intrusive rock that makes up most of the world s oceanic crust. It most commonly forms as an extrusive rock such as a lava flow but can also form in small intrusive bodies such as an igneous dike or a thin sill it has a composition similar to gabbro the difference between basalt and gabbro is that basalt is a fine grained rock while. Dacite is an extrusive igneous rock. Appearance of basalt is dull and soft and that of obsidian is shiny.

Basalt is fine grained so the individual minerals are not visible but they include pyroxene plagioclase feldspar and olivine these minerals are visible in the coarse grained plutonic version of basalt called gabbro. When obsidian breaks it fractures with a distinct conchoidal fracture. Obsidian is a very shiny natural volcanic glass. Gabbro andesite pegmatite basalt pumice porphyry obsidian granite and tuff.

Obsidian is volcanic glass meaning it has no crystals and consists primarily of silica with just enough impurities to color it whereas basalt is a low silica high iron magnesium igneous rock entirely made of small crystals of various minerals including plagioclase feldspar and usually pyroxene and or amphibole. The hardness of basalt is 6 and that of obsidian is 5 5 5. The principle minerals that make up dacite are plagioclase quartz pyroxene or hornblende. The canadian shield of north america contains huge outcroppings surface rocks of granite.

Magma that has reached the surface is lava. Associate each rock name granite diorite gabbro rhyolite andesite basalt obsidian pumice scoria tuff and volcanic breccia from the classification chart with the geological setting numbers 1 12 shown on the following diagram. Igneous rocks from left to right. Igneous rocks that solidified within the crust are plutonic or intrusive rocks.

This specimen erupted from kilauea volcano in 1960.