Basalt Granite And Obsidian Rock

Basalt is an extrusive or intrusive rock that makes up most of the world s oceanic crust.

Basalt granite and obsidian rock.

Dacite is an extrusive igneous rock. The canadian shield of north america contains huge outcroppings surface rocks of granite. This specimen erupted from kilauea volcano in 1960. Molten rock material below the surface is called magma.

When obsidian breaks it fractures with a distinct conchoidal fracture. Basalt is a dark colored fine grained igneous rock composed mainly of plagioclase and pyroxene minerals. The hardness of basalt is 6 and that of obsidian is 5 5 5. 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.

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. The principle minerals that make up dacite are plagioclase quartz pyroxene or hornblende. Obsidian is a very shiny natural volcanic glass. 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.

Igneous rocks that solidified within the crust are plutonic or intrusive rocks. Magma that has reached the surface is lava. Properties of rock is another aspect for basalt vs obsidian. Igneous rocks from left to right.

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.