Rocks

Syenite, any of a category of intrusive igneous rocks basically composed of an alkali feldspar and a ferromagnesian mineral. A unique group of alkali syenites is characterized by the presence of a feldspathoid mineral inclusive of nepheline, leucite, cancrinite, or sodalite (see nepheline syenite). Chemically, syenites comprise a slight amount of silica, incredibly big amounts of alkalies, and alumina. The call become first used by Pliny the Elder.

Granodiorite  is a phaneritic-textured intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% to 90% of the feldspar is plagioclase. A greater amount of plagioclase would designate the rock as tonalite.

An intrusive igneous rock, peridotite is coarsegrained and dense. It is light to dark green in color. Peridotite contains at least 40 percent olivine and some pyroxene. Unlike the olivine grains, the pyroxene grains in peridotite have a visible cleavage when viewed under a hand lens. Peridotite forms much of Earth’s mantle and can occur as nodules that are brought up from the mantle by kimberlite or basalt magmas.

Kimberlite is an igneous rock that major source of diamonds. Kimberlite is a variety of peridotite.  It is rich in mica minerals content and...

An important rock-forming mineral, dolomite is named after the French mineralogist Déodat Gratet de Dolomieu. It is a colorless to white, pale brown, grayish, reddish, or pink mineral. Its crystals are commonly rhombohedral or tabular, often have curved faces, and sometimes cluster in saddle-shaped aggregates.

Skarn is coarse-grained metamorphic rocks that forms by a metasomatism. Also called tactites. Skarn tend to be rich in calcium-magnesium-iron-manganese-aluminium silicate minerals that also...

Amphibolite, a rock composed in large part or dominantly of minerals of the amphibole institution. The term has been implemented to rocks of both igneous or metamorphic foundation. In igneous rocks, the term hornblendite is greater not unusual and restrictive; hornblende is the maximum not unusual amphibole and is traditional of such rocks.

Soapstone is a type of talc-schist metamorphic rock. Also other naming’s are steatite or soaprock. The composed primarily of talc, with varying amount of...

Hornfels is a fine-grained metamorphic rock These properties are because of first-class grained non-aligned crystals with platy or prismatic behavior. Hornfels is the group designation for a series of contact metamorphic rocks which have been baked and indurated by means of the warmth of intrusive igneous loads and had been rendered massive, difficult, splintery, and in a few cases exceedingly tough and sturdy.

Volcanic bomb is pyroclastic rock that is a cooling of a mass of lava it flies thorough the air after eruption. If it is...

Bauxite is a sedimentary rock mineral that is the primary source of aluminum. It is formed through the weathering of aluminum-rich rocks in tropical...

Trachyte, light-coloured, very fine-grained extrusive igneous rock that is composed chiefly of alkali feldspar with minor amounts of dark-coloured minerals such as biotite, amphibole, or pyroxene. Compositionally, trachyte is the volcanic equivalent of the plutonic (intrusive) rock syenite. Most trachytes show porphyritic texture in which abundant,