Other articles where chemical weathering is discussed: mica: Origin and occurrence: It alters rather easily during chemical weathering and thus is rare in sediments and sedimentary rocks. One stage in the weathering of biotite has resulted in some confusion. During chemical weathering, biotite tends to lose its elasticity and become decolorized …
Composed largely of calcite (a form of calcium carbonate), marble is a metamorphic rock that forms when limestone is recrystallized under the influence of heat, pressure, and chemical processes beneath Earth's surface. Encyclopædia Britannica, Inc. Marble forms from limestone, a sedimentary rock rich in calcium carbonate.
Garnet - Mineral, Crystals, Rocks: The rock-forming garnets are most common in metamorphic rocks. A few occur in igneous rocks, especially granites and granitic pegmatites. Garnets derived from such rocks occur sporadically in clastic sediments and sedimentary rocks. Typical occurrences of the common rock-forming garnets are given in …
calcite group. siderite, iron carbonate (FeCO 3 ), a widespread mineral that is an ore of iron. The mineral commonly occurs in thin beds with shales, clay, or coal seams (as sedimentary deposits) and in …
Carbonatite deposits. Carbonatites are igneous rocks that consist largely of the carbonate minerals calcite and dolomite; they sometimes also contain the rare-earth ore minerals bastnaesite, parisite, and monazite, the niobium ore mineral pyrochlore, and (in the case of the carbonatite deposit at Palabora in South Africa) copper sulfide ore minerals.The …
marble, granular limestone or dolomite (i.e., rock composed of calcium-magnesium carbonate) that has been recrystallized under the influence of heat, pressure, and aqueous solutions. Commercially, it includes all decorative calcium-rich rocks that can be polished, as well as certain serpentines (verd antiques).
Calico or laminated sandstone. Most limestones have a granular texture. Their constituent grains range in size from 0.001 mm (0.00004 inch) to visible particles. In many cases, the grains are microscopic fragments of fossil animal shells. Britannica Quiz. (Bed) Rocks and (Flint) Stones. Limestone has two origins: (1) biogenic precipitation …
Answer: Stalactites and stalagmites are elongated forms of various minerals deposited from solution by slowly dripping water. The dominant mineral in such deposits is calcite (calcium carbonate), and the largest displays are formed in caves of …
Igneous rock - Minerals, Magma, Crystals: The major mineralogical components of igneous rocks can be divided into two groups: felsic (from feldspar and silica) and mafic (from magnesium and ferrous iron). The felsic minerals include quartz, tridymite, cristobalite, feldspars (plagioclase and alkali feldspar), feldspathoids (nepheline and leucite), …
Sedimentary rock - Evaporites, Deposits, Minerals: Evaporites are layered crystalline sedimentary rocks that form from brines generated in areas where the amount of water lost by evaporation exceeds the total amount of water from rainfall and influx via rivers and streams. The mineralogy of evaporite rocks is complex, with almost 100 varieties …
Definition and Composition: Calcite is a carbonate mineral, which means it contains the carbonate ion (CO3^2-) as a fundamental building block. It is one of the …
calcite, the most common form of natural calcium carbonate (CaCO3), a widely distributed mineral known for the beautiful development and great variety of its crystals. It is … See more
Calcite is a common and widespread mineral. It is an essential and major mineral in limestones and marbles, occurs in cave deposits, and occurs as a vein mineral with other carbonates, sulfides, …
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, …
Cave - Solution, Erosion, Formations: As previously noted, the largest and most common caves are those formed by dissolution of limestone or dolomite. Limestone is composed mostly of calcium carbonate in the form of the mineral calcite. Dolomite rock consists of calcium magnesium carbonate, the mineral dolomite. Both these carbonate minerals …
It is a widely distributed mineral known for the beautiful development and great variety of its crystals. Calcium does not occur naturally in the free state, but compounds of the element are widely distributed. One calcium compound, lime (calcium oxide, CaO) was extensively used by the ancients. The silvery, rather soft, lightweight …
The mineral calcite is a form of calcium carbonate. Transparent calcite is sometimes called Iceland spar.
The term clay is generally applied to (1) a natural material with plastic properties, (2) particles of very fine size, customarily those defined as particles smaller than two micrometres (7.9 × 10 −5 inch), and (3) very fine mineral fragments or particles composed mostly of hydrous-layer silicates of aluminum, though occasionally containing ...
fluorite. simple halide. halide mineral, any of a group of naturally occurring inorganic compounds that are salts of the halogen acids ( e.g., hydrochloric acid). Such compounds, with the notable exceptions of halite (rock salt), sylvite, and fluorite, are rare and of very local occurrence.
The carbonates tend to be soft, soluble in hydrochloric acid, and have a marked anisotropy in many physical properties ( e.g., high birefringence) as a result of the planar structure of the carbonate ion. There are approximately 80 known carbonate minerals, but most of them are rare. The commonest varieties, calcite, dolomite, and …
Metamorphic rock - Zeolite Facies, Minerals, Textures: In the zeolite facies, sediments and volcanic debris show the first major response to burial. Reactions are often not complete, and typical metamorphic fabrics may be poorly developed or not developed at all. This is the facies of burial metamorphism. The zeolite facies was first described from …
mineral, naturally occurring homogeneous solid with a definite chemical composition and a highly ordered atomic arrangement; it is usually formed by inorganic processes. There are several thousand known mineral species, about 100 of which constitute the major mineral components of rocks; these are the so-called rock-forming …
Calcite is a rock-forming mineral with a chemical formula of CaCO 3. It is extremely common and found throughout the world in sedimentary, metamorphic, and igneous …
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 the Mohs scale of hardness. The degree of hardness is determined by observing the comparative ease or difficulty with which one mineral is …
Advertising Information. The Mineral calcite. Calcite is the one of the most common minerals. It occurs in a great variety of shapes and colors, and it constitutes a major portion of many of the earth's rocks. Calcite belongs …
Calcium bentonites are nonswelling and break down to a finely granular aggregate that is widely used as an absorbent clay sometimes called fuller's earth. Bentonite occurs in rocks that were deposited in the Ordovician to Neogene periods (about 488.3 to 2.6 million years ago). In the United States the principal producers are Wyoming, Montana ...
Other articles where stalagmite is discussed: stalactite and stalagmite: stalagmite, elongated forms of various minerals deposited from solution by slowly dripping water. A stalactite hangs like an icicle from the ceiling or sides of a cavern. A stalagmite appears like an inverted stalactite, rising from the floor of a cavern.
Mineral - Crystal Habit, Aggregation: The external shape (habit) of well-developed crystals can be visually studied and classified according to the various crystal systems that span the 32 crystal classes. The majority of crystal occurrences, however, are not part of well-formed single crystals but are found as crystals grown together in aggregates. Examples of …
mineral, Any naturally occurring homogeneous solid that has a definite ... Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by …
stalactite and stalagmite, elongated forms of various minerals deposited from solution by slowly dripping water. A stalactite hangs like an icicle from the ceiling or sides of a cavern. A stalagmite appears like an inverted stalactite, rising from the floor of a cavern. Stalactites hanging from the ceilings of caverns commonly exhibit a central ...
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 …
When heated, it produces carbon dioxide and calcium oxide (also called quicklime). Calcium carbonate has a molecular weight of 100.1 grams per mole. Calcium carbonate occurs naturally in three mineral forms: calcite, aragonite, and vaterite. Calcite, the most common form, is known for the beautiful development and great variety of its crystals.
Other articles where calcareous sinter is discussed: sinter: Calcareous sinter, sometimes called tufa, calcareous tufa, or calc-tufa, is a deposit of calcium carbonate, exemplified by travertine. So-called petrifying springs, not uncommon in limestone districts, yield calcareous waters that deposit a sintery incrustation on objects exposed to their action. …
Calcite, the most common form of natural calcium carbonate (CaCO3), adenine widely distributed mineral known for this beauty development and great variety to its crystallization. Computer is polymer (same chemical formula but different crystal structure) about to minerals aragonite and vaterite or with
Category: Science & Tech. trona, an evaporite mineral, hydrated sodium bicarbonate [Na 3 H (CO 3) 2 ·2H 2 O], occasionally encountered as a saline lake deposit or evaporation product and as an efflorescence on arid soil. Usually associated with natron, thermonatrite, halite, and gypsum, it occurs near Memphis, in the Lower Nile Valley; widely ...
Dolomite, type of limestone, the carbonate fraction of which is dominated by the mineral dolomite, calcium magnesium carbonate. Along with calcite and aragonite, dolomite makes up approximately 2 percent of the Earth's crust. Learn more about the structure, properties, and uses of dolomite in this article.
alstonite, a barium and calcium carbonate mineral, CaBa (CO 3) 2, with minor amounts of strontium. It is colourless or light gray or pink in appearance and is also transparent or translucent. Its crystal structure is orthorhombic and is identical to that of aragonite, with barium and calcium in nine-fold coordination but ordered within layers ...
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 defined hardness.
Sedimentary rock - Limestones, Dolomites, Carbonates: Limestones and dolostones (dolomites) make up the bulk of the nonterrigenous sedimentary rocks. Limestones are for the most part primary carbonate rocks. They consist of 50 percent or more calcite and aragonite (both CaCO3). Dolomites are mainly produced by the secondary alteration or …
The three important crystal habits (distinctive shapes of the mineral) of calcite are: (1) prismatic (both short and long), (2) rhombohedral, and (3) scalenohedral. Twinning is very common and may be of secondary origin in crystalline limestones. Some calcites fluoresce under ultraviolet light; some are also triboluminescent (luminescent when ...