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Diorite. Diorite (/ ˈdaɪ.əraɪt / DY-ə-ryte) [1][2] is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is intermediate in composition between low-silica (mafic) gabbro and high-silica (felsic) granite.
Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the feldspar in the rock consisting of plagioclase. This places andesite in the basalt /andesite field of ...
Claystone – Clastic sedimentary rock composed primarily of clay-sized particles. Coal – Combustible sedimentary rock composed primarily of carbon. Conglomerate – Sedimentary rock composed of smaller rock fragments. Coquina – Sedimentary rock that is composed mostly of fragments of shells.
Mylonite, Owl Mountains, Poland. Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.
Granite. Granite (/ ˈɡrænɪt / GRAN-it) is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Peridotite. Peridotite (US: / ˈpɛrɪdoʊˌtaɪt, pəˈrɪdə -/ PERR-ih-doh-tyte, pə-RID-ə-) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg 2+), reflecting the high proportions of ...
Graphic texture is commonly created by exsolution and devitrification and immiscibility processes in igneous rocks. It is called 'graphic' because the exsolved or devitrified minerals form lines and shapes which are reminiscent of writing. Graphic granite is a leucocratic granitic rock consisting of alkali feldspar with exsolved quartz ...
It is an igneous rock. [6] Obsidian is produced from felsic lava, rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows. These flows have a high content of silica, granting them a high viscosity.