Type of Rocks
Source: 
www.geology.com
www.wikipedia.org
Igneous rock (derived from the Latin word ignis meaning fire) is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust.

What is Diorite?
Diorite is a coarse-grained, intrusive igneous rock that is intermediate in composition between granite and gabbro. It’s composition is very similar to the fine-grained extrusive rock known as andesite.
Diorite is composed primarily of plagioclase feldspar, amphibole, and pyroxine minerals with small amounts of biotite mica. It typically contains very little quartz.
When identifying diorite look for a rock that as abundant white and dark minerals - a “salt and pepper” appearance. With a hand lens look for the cleavage faces of plagioclase feldspar intersecting at oblique angles. Also, look for vitreous cleavage faces on the dark amphibole minerals.
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What is Basalt?
Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. 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 gabbro is a coarse-grained rock.




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What is Andesite ?
Andesite is a fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene and biotite. 







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What is Rhyolite ?
Rhyolite is a light-colored, fine-grained, extrusive igneous rock that typically contains quartz and feldspar minerals.







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What is tuff ?
Tuff is an igneous rock that forms from the products of an explosive volcanic eruption. In these eruptions the volcano blasts rock, ash, magma and other materials from its vent. This ejecta travels through the air and falls back to Earth in the area surrounding the volcano. If the ejected material is compacted and cemented into a rock that rock will be called "tuff". Read more ...



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What is Granite ?
Granite is a light-colored igneous rock with grains large enough to be visible with the unaided eye.  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 grains visible throughout the rock.



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What is Scoria ?
Scoria is a dark-colored igneous rock with abundant round bubble-like cavities known as vesicles. It ranges in color from black or dark gray to deep reddish brown. Scoria usually has a composition similar to basalt, but can also have a composition similar to andesite. Many people believe that small pieces of scoria look like the ash produced in a coal furnace. That has resulted in particles of scoria being called "cinders" and the small volcanoes that erupt scoria to be called "cinder cones". Read more ...


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What is Pumice ?
Pumice is a light-colored, extremely porous igneous rock that forms during explosive volcanic eruptions. It is used as aggregate in lightweight concrete, as landscaping aggregate, and as an abrasive in a variety of industrial and consumer products. Many specimens have a high enough porosity that they can float on water until they slowly become waterlogged. Read More...



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What is Peridotite ?
Peridotite is a generic name used for coarse-grained, dark-colored, ultramafic igneous rocks. Peridotites usually contain olivine as their primary mineral, frequently with other mafic minerals such as pyroxenes and amphiboles. Their silica content is low compared to other igneous rocks and they contain very little quartz and feldspar. Peridotites are economically important rocks because they often contain chromite - the only ore of chromium; they can be source rocks for diamonds; and, they have the potential to be used as a material for sequestering carbon dioxide. Much of Earth's mantle is believed to be composed of peridotite.

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What is Gabbro ?
Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust. Gabbro has a variety of uses in the construcion industry. It is used for everything from crushed stone base materials at construction sites to polished stone counter tops and floor tiles.

What Minerals are in Gabbro?
Gabbro is composed mainly of calcium-rich plagioclase feldspar (usually labradorite or bytownite) and clinopyroxene (augite). Minor amounts of olivine and orthopyroxene might also be present in the rock. 
---------------------------------------------------------------------------------------What is Recitulite?
RETICULITE -- Frothy basaltic rock sometimes called basalt pumice or thread-lace scoria. This delicate rock forms during vigorous fire-fountaining. Reticulite has the lowest density of any rock, with a porosity (vesicularity) up to 98 percent. The open honeycomb network of bubbles (vesicles) results from the bursting of cell walls against one another during vesiculation.