rock name/ rocks

schist

A schist is a medium to coarse-grained, foliated, metamorphic rock t

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".

pegmatite

A light (felsic) igneous rock that is very coarse-grained.

Amphibolite

Amphibolite is a coarse-grained metamorphic rock that is composed mainly of green, brown or black amphibole minerals and plagioclase feldspar. Amphibolite is a rock of convergent plate boundaries where heat and pressure cause regional metamorphism.

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.

chert

Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges.

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,

mudstone

Mudstone is an extremely fine-grained sedimentary rock consisting of a mixture of clay and silt-sized particles.

breccia

Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. ( differs from conglomerate by having angular rather then round large particles)

marble

Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) Under the conditions of metamorphism the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals.

pumice

Pumice is a light-colored, extremely porous igneous rock that forms during explosive volcanic eruptions.The pore spaces (known as vesicles) in pumice are a clue to how it forms. The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure. Thus, pumice is an amorphous volcanic glass known as a "mineraloid".

quartzite

Quartzite is a nonfoliated metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone, is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together. The result is a network of interlocking quartz grains of incredible strength.

slate

Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism

limestone

Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite.

dolerite

A dolerite is the medium-grained equivalent of a basalt - a basic rock dominated by plagioclase and pyroxene.

andesite

Andesite is the name used for a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color.

conglomerate

Conglomerate is a clastic sedimentary rock that contains large (greater than two millimeters in diameter) rounded clasts. The space between the clasts is generally filled with smaller particles and/or a chemical cement that binds the rock together.

diorite

Diorite is the name used for a group of coarse-grained igneous rocks with a composition between that of granite and basalt. It usually occurs as large intrusions, dikes, and sills within continental crust.Diorite is usually composed of sodium-rich plagioclase with lesser amounts of hornblende and biotite.

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.

gneiss

Gneiss is a foliated metamorphic rock identified by its bands and lenses of varying composition, while other bands contain granular minerals with an interlocking texture. Other bands contain platy or elongate minerals with evidence of preferred orientation. It is this banded appearance and texture - rather than composition - that define a gneiss. Gneiss usually forms by regional metamorphism at convergent plate boundaries.

hornfels

Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was "baked" while near a heat source such as a magma chamber, sill or dike.

obsidan

Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure. It is an amorphous material known as a "mineraloid." The result is a volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture

phyllite

Phyllite is a type of foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation.

rhyolite

Rhyolite is an extrusive igneous rock with a very high silica content. It is usually pink or gray in color with grains so small that they are difficult to observe without a hand lens.Many rhyolites form from granitic magma that has partially cooled in the subsurface.

sandstone

Sandstone is a sedimentary rock composed of sand-sized grains of mineral, rock or organic material. It also contains a cementing material that binds the sand grains together and may contain a matrix of silt- or clay-size particles that occupy the spaces between the sand grains.

shale

Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call "mud". This composition places shale in a category of sedimentary rocks known as "mudstones". Shale is distinguished from other mudstones because it is fissile and laminated. "Laminated" means that the rock is made up of many thin layers. "Fissile" means that the rock readily splits into thin pieces along the laminations.

siltstone

Siltstone is a sedimentary rock composed mainly of silt-sized particles. It forms where water, wind, or ice deposit silt and the silt is then compacted and cemented into a rock.