Definitions

1. Rocks are either SEDIMENTARY, IGNEOUS, or METAMORPHIC. Almost all rocks made of minerals, but different rocks contain different mixtures of minerals. (Web site)
2. Rocks are identified by the minerals they contain and are grouped according to their origin into three major classes: sedimentary, igneous, and metamorphic. (Web site)
3. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic. (Web site)
4. Rocks are generally classified by the processes that formed them, and are thus separated into igneous, sedimentary, and metamorphic rocks.
5. Rocks are divided into three basic types, igneous, sedimentary and metamorphic, depending upon how they were formed. (Web site)

Grain Size

1. Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix) composition, and texture. (Web site)
2. Metamorphic rocks are classified by texture (foliation and grain size) and mineral content.

Texture

1. For example, the texture of igneous rocks tells us where the rocks formed on the earth.
2. PART I. Group all of the rocks, on the basis of texture, into three groups: volcanic, plutonic, or porphyritic. (Web site)
3. The texture of syenites, like that of granite, is granular, and these rocks differ from granite only by the absence or scarcity of quartz. (Web site)

Feldspar

1. Most rocks are composed of several different minerals; e.g., granite consists of feldspar, quartz, mica, and amphibole.
2. Rocks and minerals rich in silicon are called silica-rich or felsic (rich in feldspar and silica).
3. Rocks on the left, like granite and rhyolite, contain abundant quartz (up to 25%) and feldspar (10%, with potassium feldspar dominant).

Granitic Rocks

1. In the diagram here, broad families of rocks (granitic rocks, syenite, gabbro) are shown by common colors. (Web site)
2. Continental crust is composed of granitic rocks which are made up of relatively lightweight minerals such as quartz and feldspar.
3. Granitic rocks may include epidote, tourmaline, beryl, apatite, topaz, zircon, and sphene A pea-green mineral in granitic rocks is almost always epidote.

Hornblende

1. Amphibolite is a gouping of rocks composed mainly of amphibole (as hornblende) and plagioclase feldspar s, with little or no quartz.
2. Although the rocks are locally chloritized and epidotized, varying amounts of biotite, hornblende and quartz are present in the sections. (Web site)
3. Plutonic rocks are primarily comprised of 5 minerals: quartz, potassium feldspar, plagioclase feldspar, biotite, and hornblende. (Web site)

Olivine

1. These rocks contain also iron oxides (usually titaniferous), apatite, sometimes sphene, augite, and olivine.
2. Serpentinization is the alteration of olivine to serpentine (with magnetite); it is typical of peridotites, but occurs in most of the mafic rocks.
3. Mafic Igneous rocks which are rich in the minerals of pyroxene and olivine. (Web site)

Limestones

1. During a volcanic eruption, then, lavas and pyroclastics may interbed with limestones to form a very unusual association of rocks. (Web site)
2. Examples of sedimentary rocks are limestones, sandstones, and shales. (Web site)
3. The Ordovician rocks comprise flaggy shales, limestones, red quartzites, quartzites, sandstones and conglomerates. (Web site)

Schists

1. In order to more explicitly identify samples of the rocks, schists are typically classified and described based upon their mineralogical composition. (Web site)
2. The muscovite-based type of sericite most often occurs in phyllites, schists, and other rocks that exhibit a fine-grained, layered structure. (Web site)
3. Amphiboles occur in many igneous rocks as minor and major constituents and form the major component in many gneisses and schists. (Web site)

Strain

1. Earthquakes occur when energy stored within the Earth, usually in the form of strain in rocks, suddenly releases. (Web site)
2. This theory states that during an earthquake, the rocks under strain suddenly break, creating a fracture along a fault.
3. The strain becomes so great that rocks give way by breaking and sliding along fault planes.

Mineralogy

1. Petrology utilizes the classical fields of mineralogy, microscopic petrography, and chemical analyses to describe the composition and texture of rocks.
2. Petrology is the science of rocks: their mineralogy, textures, chemistry, classification, and structures.
3. This has altered the mineralogy, texture and chemical composition of the rocks. (Web site)

Petrology

1. The study of rocks is called (A) geology, (B) petrology, (C) mineralogy, or (D) paleontology.
2. Petrology is a field of geology which focuses on the study of rocks and the conditions by which they form.
3. There are three branches of petrology, associated with three types of rocks: frozen, metamorphic, and sedimentary. (Web site)

Biotite

1. Epidotization occurs also in rocks of this group, and consists in the development of epidote from biotite, hornblende, augite or plagioclase feldspar.
2. The final assemblage we can establish in these rocks is biotite + andalusite + K-feldspar + plagioclase + ilmenite + quartz (Assemblage 3).
3. All rocks will likely contain mafic minerals such as biotite, hornblende, and perhaps pyroxenes, along with opaque oxide minerals.

Quartz

1. The metamorphic mineral assemblages in the rocks of the eastern inclusion consist of quartz, plagioclase, biotite, and sometimes actinolite or hornblende.
2. Stop #1: The rocks exposed at Snoqualmie Pass are coarse grained (crystals are all about 5 mm long) and are made of quartz, orthoclase, and biotite. (Web site)
3. Alteration Host rocks contain quartz + siderite and (or) ankerite + tourmaline + chlorite + magnetite in mafic volcanic terranes. (Web site)

Mafic

1. Intermediate rocks have qulaities of both felsic and mafic rocks, examples include andesite and diorite.
2. That magma crystallizes to mafic rocks such as gabbro and basalt. (Web site)
3. Mafic rocks are black, dark gray or dark green in color, and composed primarily of olivine, feldspar (calcium plagioclase) and pyroxene.

Ultramafic Rocks

1. Olivine in mafic and ultramafic rocks typically is rich in the forsterite end-member.
2. Oceanic lithosphere consists mainly of mafic and ultramafic rocks and is denser than continental lithosphere, which consists predominantly of felsic rocks.
3. Small and isolated intrusions of diorite, gabbro, gabbronorite, ultramafic rocks, monzonite, syenite and anorthosite constitute about 2% of the area.

Sandstone

1. Quartz - Quartz is a very hard mineral composed of silica, found worldwide in many different types of rocks, including sandstone and granite. (Web site)
2. The exposed rocks in the municipality are mostly composed of sandstone, limestone, shale, and a few coal layers (Redstone, Waynesburg, Washington, etc.). (Web site)
3. Sandstone - like shale, this is a clastic or detrital sedimentary rock-- originating from the weathering and breakdown of other rocks. (Web site)

Clastic Sedimentary Rocks

1. Clastic sedimentary rocks are made up of fragments of other rocks and include sandstone, conglomerate, and shale. (Web site)
2. Clastic Sedimentary Rocks are those that are composed of fragments of other rocks (igneous, metamorphic, sedimentary). (Web site)
3. Clastic sedimentary rocks are the group of rocks most people think of when they think of sedimentary rocks.

Mineral Composition

1. The description of rocks on the basis of color, structure, mineral composition, and grain size; the physical character of a rock.
2. Lithology is the study of rocks, emphasizing their macroscopic physical characteristics, including grain size, mineral composition, and color. (Web site)
3. Lithology: The study and description of rocks, including their mineral composition and texture. (Web site)

Extrusive

1. Extrusive rocks are fine-grained in texture and crystallise quickly from lava on or near the earth's surface.
2. In the case of extrusive rocks, the answer is obvious: we can see basalt (for example) forming when lava flows cool; there is no difficulty there.
3. Small-grained rocks generally form from volcanic eruptions and are often referred to as extrusive rocks; they are also called aphanitic. (Web site)

Gneisses

1. As a result, the rocks produced are often strongly foliated slates, schists, or gneisses.
2. Sphene occurs as an accessory mineral in igneous rocks, notably nepheline syenites, and in gneisses, schists, and marbles.
3. Rutile is found as an accessory mineral in many kinds of igneous rocks, and to some extent in gneisses and schists. (Web site)

Gneiss

1. In general, the granitic terrain contains good aquifers as compared to gneiss, schist, jphyllite, slate, pegmatities, dolerites, volcanic (igneous) rocks. (Web site)
2. Kyanite forms during regional metamorphism under elevated temperatures and pressures, in rocks such as gneiss and schist. (Web site)
3. Many metamorphic rocks are highly foliated, such as slate, phyllite, schist, and gneiss.

Volcanic

1. These rocks are formed at a depth in between the plutonic and volcanic rocks.
2. Geologically, Mangaia contains the oldest exposed volcanic rocks on the Pacific plate, with some its rocks being dated with ages of over 19 million years.
3. Most maars have low rims composed of a mixture of loose fragments of volcanic rocks and rocks torn from the walls of the diatreme. (Web site)

Plutonic Rocks

1. Alkaline rocks are more common in volcanic and hypabyssal facia, and less abundant as plutonic rocks. (Web site)
2. The Grenville sediments were intruded by a series of plutonic rocks, the oldest of which were gabbro, diorite and ultrabasic rocks.
3. Quartz diorite, diorite and gabbro are plutonic rocks found in Yosemite, but are not technically considered to be granitic rocks. (Web site)

Plutonic

1. Rocks that form in this way are called intrusive igneous or plutonic rocks. (Web site)
2. Although feldspathoids are known to both extrusive and intrusive igneous rocks, cancrinite is found almost exclusively in intrusive or plutonic rocks. (Web site)
3. Based on their mode of occurrence, igneous rocks are either intrusive or plutonic rocks and extrusive or volcanic rocks. (Web site)

Intrusive Rocks

1. Intrusive rocks are coarse-grained in texture and crystallise slowly from magma deep in the earth's crust.
2. Slow cooling allows individual mineral crystals to grow large enough that we can see them without a magnifying lens, so intrusive rocks are coarse-grained. (Web site)
3. The crystals in intrusive rocks are larger because the magma that forms them is insulated by the surrounding rock and therefore cools slowly.

Geologists

1. Geologists examine the composition, processes and history of the Earth to learn how rocks were formed and what has happened since formation.
2. Geologists classify rocks into three main categories - sedimentary, igneous, and metamorphic - based on the way in which they form. (Web site)
3. In the 19th century, geologists recognized that many rocks preserve the imprint of Earth's magnetic field as it was at the time of their formation.

Fossils

1. Geologists have divided the history of the Earth into Eons (the largest division), Eras, Periods, and Epochs, mostly based on the fossils found in rocks.
2. The fossils of animals are rare in these rocks, and those that can be found are simple. (Web site)
3. In rocks of the Mesozoic era, gastropods are slightly more common as fossils, their shells are often well preserved.

Pre-Existing Rocks

1. This magma can be derived from partial melts of pre-existing rocks in either the Earth 's mantle or crust. (Web site)
2. Hydrothermal alteration: Alteration of rocks or minerals by the reaction of hot water (and other fluids) with pre-existing rocks. (Web site)
3. This magma can be derived from partial melts of pre-existing rocks in either a planet 's mantle or crust.

Weathering

1. Layers of soil and other rocks above intrusive igneous rocks are often worn away due to erosion and weathering. (Web site)
2. Most weathering occurs at the surface, but it may take place deep under the surface as water and oxygen penetrates into rocks through joints. (Web site)
3. Rocks exposed to the atmosphere are variably unstable and subject to the processes of weathering and erosion.

Intrusive

1. Igneous rocks which form by the crystallization of magma at a depth within the Earth are called intrusive rocks.
2. The big four of intrusive rocks are with increasing silica: gabbro, diorite, granodiorite, and granite. (Web site)
3. Intrusive rocks crystallize from magmas that have been intruded into the earth's crust at depths far below the surface.

Extrusive Rocks

1. Rocks formed at the surface of the earth are called extrusive rocks.
2. In extrusive rocks, where cooling is much more rapid, the individual mineral crystals are usually not visible and these rocks are termed aphanitic.
3. Extrusive rocks are formed on the surface of the Earth from volcanic activity. (Web site)

Basalt

1. The volcanics in the backarc basin begin mafic (basalt, scoria, etc.), but slowly turn into intermediate (andesite), and finally felsic (rhyolite) rocks. (Web site)
2. Characteristic chemical trends relate compositions of rocks as arranged in a series from basalt to rhyolite (intrusive equivalents from gabbro to granite).
3. Rocks on the right, like gabbro and basalt, contain abundant iron-magnesium rich minerals such as pyroxene, amphibole and olivine.

Volcanic Rocks

1. The volcanic rocks outside the park include these same rocks as well as ash-flow tuff, rhyolite, pumice, obsidian, etc. (Web site)
2. Depending on conditions present during eruption and cooling, any of these rock types may form one of the following types of volcanic rocks. (Web site)
3. Volcanic rocks, the solidified products of volcanic eruptions are part of a larger group of rocks called igneous rocks. (Web site)

Schist

1. Compare your rocks to those already identified as metamorphic like quartzite, hornfels and marble, slate, schist and gneiss. (Web site)
2. Squeezed rocks such as slate, schist, and gneiss have their minerals reoriented and realigned at right angles to the pressure.
3. Some types of metamorphic rocks are slate, phyllite, schist, gneiss, marble, quartzite, hornfels, migmatite, mylonite, metaconglomerate and amphibolite.

Metamorphism

1. During metamorphism, rocks which were originally sedimentary or igneous are converted into schists and gneisses. (Web site)
2. Metamorphic petrology: the study of the effects of metamorphism on minerals and rocks. (Web site)
3. Metamorphism: Changes over time, in the composition and structure of rocks caused by pressure and temperature.

Granite Rocks

1. Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. (Web site)
2. The upper part mainly consists of granite rocks, while the lower part consists of basalt and diorite.
3. It occurs in granite rocks, pegmatites, and in mica schists.

Granites

1. Quite common, hornblendes are associated with a wide variety of rocks, such as syenites, granites, gneisses, and gabbros. (Web site)
2. Relatively rare, syenites are much less common than granites, diorites, and many other rocks. (Web site)
3. Some granites are the oldest known rocks on earth; others were formed during younger geologic periods. (Web site)

Granite

1. Gneiss may form from diorite, granite, shale, sandstone, schist or other rocks. (Web site)
2. Besides, albite, biotite, muscovite and hornblende are also found in granite rocks.
3. This is because oceanic crust is made of basalt, which is denser (heavier) than the granite rocks that compose continental crust. (Web site)

Metamorphic

1. Quantitatively, the metamorphic rocks, including gneisses and migmatites, are the most important group of rocks in the crust of the continents. (Web site)
2. Rocks that form from the alteration of existing rocks by heat, pressure, and chemical change are metamorphic rocks.
3. Metamorphic rocks are the least common of the 3 kinds of rocks. (Web site)

Sedimentary

1. Gneisses result from the metamorphism of many igneous or sedimentary rocks, and are the most common types of rocks found in Precambrian regions. (Web site)
2. Generally speaking, these rocks are formed from the alteration of igneous and sedimentary rocks through heat and pressure. (Web site)
3. Rocks such as slate, phyllite, schist and gneiss are formed from sedimentary rocks called shales.

Magma

1. Olivine forms from magma that is rich in magnesia and low in silica, forming such rocks as gabbro, norite, peridotite and basalt. (Web site)
2. Igneous rocks which form by the crystallization of magma at the surface of the Earth are called extrusive rocks. (Web site)
3. Igneous rocks that are formed by solidification of lava are known as extrusive and those formed by magma at shallow depths of the Earth are called intrusive.

Igneous

1. Igneous rocks are one of the three main types of rocks; the other types are sedimentary rocks and metamorphic rocks.
2. MOLTEN material within the Earth is called MAGMA, and is the parent material for a great many rocks collectively known as IGNEOUS ROCKS. (Web site)
3. Geologists, scientists who study Earth and rocks, divide rocks into three main groups: igneous rocks, sedimentary rocks, and metamorphic rocks. (Web site)

Metamorphic Rock

1. Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock. (Web site)
2. Igneous and sedimentary rocks become metamorphic rock as a result of intense heat from magma and pressure from burial within Earth. (Web site)
3. Rocks below Earth's surface may melt and form magma, and the cycle repeats.For example, marble is a metamorphic rock that once was limestone. (Web site)

Metamorphic Rocks

1. Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss, and schist. (Web site)
2. Above 700 degrees, the rock can take on magma-like properties, leading some rocks to appear as if they have layers of igneous and metamorphic rocks. (Web site)
3. It also occurs in igneous and metamorphic rocks chiefly in the silicate minerals: plagioclase, amphiboles, pyroxenes and garnets.

Igneous Rock

1. Types of Rocks Besides basalt, examples of igneous rock are granite and obsidian.
2. A fourth category of igneous rock is those rocks that cooled too quickly for minerals to form and are glassy in texture.
3. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. (Web site)

Igneous Rocks

1. Igneous rocks These rocks are formed by direct cooling of the molten material of the earth resulting in crystallization of minerals.
2. These rocks include volcanic rocks, igneous rocks of dykes and sills and plutonic rocks such as granite, syenite, gabbro and ultramafic rocks. (Web site)
3. Igneous rocks (etymology from Latin ignis, fire) are rocks formed by solidification of cooled magma (molten rock). (Web site)

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1. Encyclopedia of Keywords > Nature > Natural Resources > Minerals
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Subcategories

Igneous Rocks (6)

Metamorphic Rocks (6)

Sedimentary Rocks (1)

Bedrock Boulder Conglomerates Coprolite

Desert Varnish Dunite Lapilli Laterite

Latite Metasomatism Meteorites Monzonite

Mudstone Nephelinite Norite Pebble

Phonolite Serpentinite Volcanic Rocks Tephra

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