Articles from Britannica Encyclopedias for elementary and high school students. sedimentary rock - Children's Encyclopedia (Ages 8-11) sedimentary rock - Student Encyclopedia (Ages 11 and up) ... mainly transported, sand-size minerals such as quartz and feldspar, (2) a detrital matrix of clay or mud, which is absent in "clean" …
Other articles where sagenite is discussed: rutile: …rutile in quartz are called sagenite (from the Greek word for "net"). Hairlike crystals of rutile not included in quartz are rare; the quartz crystals mechanically enclose the rutile during growth. Most fine-quality rutilated quartz comes from Minas Gerais, Brazil; Madagascar; Hanover, New Hampshire; and …
Quartz is a mineral that is composed of silicon and oxygen atoms in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall …
Agate, common semiprecious silica mineral, a variety of chalcedony that occurs in bands of varying colour and transparency. Agate is essentially quartz, and its physical properties are in general those of that mineral. See silica mineral (table). Agate is found throughout the world. In the United
Sandstone, lithified accumulation of sand-sized grains (0.063 to 2 mm [0.0025 to 0.08 inch] in diameter). It is the second most common sedimentary rock after shale, constituting about 10 to 20 percent of the …
quartz, Second most abundant mineral (after feldspar) in the Earth's crust, present in many rocks. Quartz, which consists of silica, or silicon dioxide (SiO 2 ), has great economic …
Talc, common silicate mineral that is distinguished from almost all other minerals by its extreme softness. Its soapy or greasy feel accounts for the name soapstone given to compact aggregates of talc and other rock-forming minerals. Dense aggregates of high-purity talc are called steatite.
Olivine, any member of a group of common magnesium, iron silicate minerals. Olivines are an important rock-forming mineral group. Magnesium-rich olivines are abundant in low-silica mafic and ultramafic igneous rocks and are believed to be the most abundant constituent of the Earth's upper mantle.
Quartzite, sandstone that has been converted into a solid quartz rock, free from pores and possessing a smooth fracture. Quartzite, when struck, breaks through, not around, the sand grains. The conversion of sandstone to quartzite may occur by precipitation of silica from interstitial waters below Earth's surface.
Quartz is the second most abundant mineral in Earth's crust after feldspar. It occurs in nearly all acid igneous, metamorphic, and sedimentary rocks. It is an essential mineral in such silica-rich felsic rocks as granites, granodiorites, and rhyolites.
sand, mineral, rock, or soil particles that range in diameter from 0.02 to 2 mm (0.0008–0.08 inch). Most of the rock-forming minerals that occur on the Earth's surface are found in sand, but only a limited number are common in this form. Although in some localities feldspar, calcareous material, iron ores, and volcanic glass are dominant …
Metamorphic rock, any rock that results from the alteration of preexisting rocks in response to changing conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks.
Mineral - Chemical Bonding, Structure, Properties: Electrical forces are responsible for the chemical bonding of atoms, ions, and ionic groups that constitute crystalline solids. The physical and chemical properties of minerals are attributable for the most part to the types and strengths of these binding forces; hardness, cleavage, …
Traditional ceramics, ceramic materials that are derived from common, naturally occurring raw materials such as clay minerals and quartz sand. Through industrial processes that have been practiced in some form for centuries, these materials are made into such familiar products as china tableware,
Mineral - Polymorphism, Crystalline Structure, Chemical Compounds: Polymorphism is the ability of a specific chemical composition to crystallize in more than one form. This generally occurs as a response to changes in temperature or pressure or both. The different structures of such a chemical substance are called polymorphic …
Mineral - Crystal Structures, Chemical Compounds: The external morphology of a mineral is an expression of the fundamental internal architecture of a crystalline substance—i.e., its crystal structure. The crystal structure is the three-dimensional, regular (or ordered) arrangement of chemical units (atoms, ions, and anionic groups in inorganic …
Chalcedony, a very fine-grained (cryptocrystalline) variety of the silica mineral quartz (q.v.). A form of chert, it occurs in concretionary, mammillated, or stalactitic forms of waxy lustre and has a compact fibrous structure, a fine splintery fracture, and a great variety of colours—usually
Limestone, sedimentary rock composed mainly of calcium carbonate, usually in the form of calcite or aragonite. It may contain considerable amounts of magnesium carbonate (dolomite) as well; minor constituents also commonly present include clay, iron carbonate, feldspar, pyrite, and quartz.
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. ... Minerals combine with each other to form rocks. For example, granite consists of the minerals feldspar, quartz, mica, and amphibole in ...
Sedimentary rock - Limestones, Dolomites, Calcite: Limestones and dolomites are collectively referred to as carbonates because they consist predominantly of the carbonate minerals calcite (CaCO3) and dolomite (CaMg[CO3]2). Almost all dolomites are believed to be produced by recrystallization of preexisting limestones, although the …
Geology - Earth Composition, Rocks, Minerals: As a discipline, mineralogy has had close historical ties with geology. Minerals as basic constituents of rocks and ore deposits are obviously an integral aspect of geology. The problems and techniques of mineralogy, however, are distinct in many respects from those of the rest of geology, …
Other articles where authigenic mineral is discussed: sedimentary rock: Mineralogical and geochemical composition: …two principal types—namely, detrital and authigenic. Detrital minerals, such as grains of quartz and feldspar, survive weathering and are transported to the depositional site as clasts. Authigenic minerals, like calcite, halite, and gypsum, …
Mineral - Hardness, Mohs Scale, Crystalline: Hardness (H) is the resistance of a mineral to scratching. It is a property by which minerals may be described relative to a standard scale of 10 minerals known as …
Pyrite, a naturally occurring iron disulfide mineral. The name comes from the Greek word pyr, 'fire,' because pyrite emits sparks when struck by metal. Pyrite is called fool's gold; to the novice its color is deceptively similar to that of a gold nugget.
MINERAL meaning: 1 : a substance (such as quartz, coal, petroleum, salt, etc.) that is naturally formed under the ground; 2 : a chemical substance (such as iron or zinc) that occurs naturally in certain foods and that is important for good health
The two most common chemical elements in the Earth's crust, oxygen and silicon, combine to form the mineral quartz, the second most abundant mineral after feldspar.
Encyclopædia Britannica, Inc. ... One of the most common minerals, quartz occurs in many areas in a variety of forms. Semiprecious gem stones of quartz include amethyst, tigereye, agate, and onyx. Siliceous sinter, or geyserite, is an impure quartz deposited by hot springs and is a form of opal. The fire opal has an internal iridescence of ...
The formation of sand from quartz, which originates from igneous processes, and the role that weathering plays in making individual sand grains more transportable by water currents.
The two most common chemical elements in the Earth's crust, oxygen and silicon, combine to form the mineral quartz, the second most abundant mineral after feldspar. Quartz…
Mohs hardness, rough measure of the resistance of a smooth surface to scratching or abrasion, expressed in terms of a scale devised (1812) by the German mineralogist Friedrich Mohs. The Mohs hardness of a mineral is determined by observing whether its surface is scratched by a substance of known or