Chalk is a soft, white, porous form of limestone composed of the mineral calcium carbonate. It is relatively resistant to erosion and slumping compared to the clays that it is usually associated with, and so forms tall steep cliffs where chalk ridges meet the sea. Chalk hills, known as chalk downland, usually form where bands of chalk reach the surface at an angle. Chalk is formed in shallow waters by the gradual accumulation of the calcite mineral remains of micro-organisms over millions of years. Embedded fli ...

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Sapphire is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. It can be found naturally as gemstones or manufactured in large crystal boules for a variety of applications. Sapphire - Sapphire gems. Sapphire is any gemstone-quality corundum. (The red variety of corundum is also known as ruby.) When color is not specified, sapphire refers to the blue variety. Pink, yellow, green, white, and parti-color (multi-colored) sapphires are oft ...

Including:

• Sapphire - Sapphire gems
• Sapphire - Synthetic sapphire for non-gemstone applications

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A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone. Quarries are usually shallower than other types of open-pit mines. People in some English-speaking countries are unlikely to make the distinction between this type of mine and any other type of open-pit or open-cast borrow or gravel pit mining operation. Quarries in level areas often have special engineering problems for drainage. The coquina quarry at the ...

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Antigorite is a monoclinic mineral from the kaolinite-serpentine group. It is a polymorph of clinochrysotile, lizardite, orthochrysotile and parachrysotile. It was first described and got its name from the Antigorio valley, Novara province, Piedmont, Italy. See also: List of minerals Other related archivesItaly, List of minerals, Piedmont, clinochrysotile, kaolinite, lizardite, mineral, monoclinic, orthochrysotile, parachrysotile, polymorph, serpentine

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Fluorite (also called fluor-spar) is a mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Crystal twinning is common and adds complexity to the observed crystal habits. Fluorite - Occurrence. Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the worthless "host-rock" in which valuable minerals occur) and may be ...

Including:

• Fluorite - Occurrence
• Fluorite - Fluorescence
• Fluorite - Blue John
• Fluorite - Uses
• Fluorite - Gallery

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The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). It gives its name to the group of minerals with a related structure (the olivine group) which includes monticellite and kirschsteinite. Olivine occurs in both mafic and ultramafic igneous rocks, and as a primary mineral in certain metamorphic rocks. It is one of the most common minerals on Earth, ...

Including:

• Olivine - Identification and paragenesis
• Olivine - Crystal structure
• Olivine - High pressure polymorphs and phase diagram

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Chlorite is a group of phyllosilicate minerals often classified as clays. Chlorites can be described by the following four endmembers based on the metals: Mg, Fe, Ni, and Mn. Clinochlore: (Mg5Al)(AlSi3)O10(OH)8 Chamosite: (Fe5Al)(AlSi3)O10(OH)8 Nimite: (Ni5Al)(AlSi3)O10(OH)8 Pennantite: (Mn,Al)6(Si ...

Including:

• Chlorite group - Chlorite structure
• Chlorite group - Occurrence
• Chlorite group - Members of the Chlorite group:

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Blue Amber is a rare coloration of amber. It most commonly is found in the Dominican Republic and well regarded by collectors for its value. Blue Amber - Origin. It is not fully understood what causes the blue coloration. One theory links the rare properties to the occurrence of volcanic ash or dust which was present when the resin was first pressed out from Hymenaea protera millions of years ago. Another suggests that due to volcanic activity hot lava must have flown over those areas where regular a ...

Including:

• Blue Amber - Origin
• Blue Amber - Is it really blue?

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Clay is a generic term for an aggregate of hydrous silicate particles less than 4 μm (micrometres) in diameter. Clay consists of a variety of phyllosilicate minerals rich in silicon and aluminium oxides and hydroxides which include variable amounts of structural water. Clays are generally formed by the chemical weathering of silicate-bearing rocks by carbonic acid, but some are formed by hydrothermal activity. Clays are distinguished from other small parti ...

Including:

• Clay - Historical and modern uses of clay

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The mineraloid opal is amorphous SiO2·nH2O; hydrated silicon dioxide, the water content sometimes being as high as 20%. Opal ranges from colorless through white, milky blue, gray, red, yellow, green, brown and black. Often many of these colors can be seen at once, caused by interference and diffraction of light passing through minute, regularly arranged apertures within the microstructure of opal, known as Bragg's lattice. These apertures are filled with secondary silica and form thin lamellae insi ...

Including:

• Opal - Common opal
• Opal - Sources of opal
• Opal - Synthetic opal

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To be classified as a "true" mineral, a substance must be a solid and have a crystal structure. It must also be an inorganic, naturally-occurring, homogenous substance with a defined chemical composition. The chemical composition may vary between end members of a mineral system. For example the plagioclase feldspars comprise a continuous series from sodium-rich albite (NaAlSi3O8) to calcium-rich anorthite (CaAl2Si2O8) with four recognized intermediate compositions between. Mineral-like s ...

See also:

Mineral, Mineral - Mineral definition and classification, Mineral - Minerals and rocks, Mineral - Physical properties of minerals, Mineral - Chemical properties of minerals

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Some mineral deposits are formed, improved, or preserved by geologic processes that occur in arid lands as a consequence of climate. Ground water leaches ore minerals and redeposits them in zones near the water table. This leaching process concentrates these minerals as ore that can be mined. Evaporation in arid lands enriches mineral accumulation in their lakes. Playas may be sources of mineral deposits formed by evaporation. Water evaporating in closed basins precipitates minerals such as gypsum, salts (including sodium nitrate and ...

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Desert, Desert - Types of desert, Desert - Montane deserts, Desert - Desert features, Desert - Soils, Desert - Vegetation, Desert - Water, Desert - Mineral resources, Desert - List of deserts, Desert - Americas, Desert - Africa, Desert - Asia-Pacific, Desert - Other

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There are over 130 species of minerals that have been cut into gems with 50 species in common use. These include: Agate Alexandrite and other varieties of chrysoberyl Amethyst (originally a "cardinal gem", but now no longer so, since huge quantities were discovered in Brazil and the price plummeted) Aquamarine and other varieties of beryl Chrysocolla Chrysoprase Diamond Emerald Feldspar (moonstone) Garnet Hematite Jade - jadeite an ...

See also:

Gemstone, Gemstone - Characteristics and classification, Gemstone - Value, Gemstone - Factors Influencing Esteem, Gemstone - Synthetic and artificial gemstones, Gemstone - Gemstone list

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Zircon is a remarkable mineral, if only for its almost ubiquitous presence in the crust of Earth. It is found in igneous rocks (as primary crystallization products), in metamorphic rocks (as recrystallized grains) and in sedimentary rocks (as detrital grains). Large zircon crystals are seldom abundant. Their average size, e.g. in granite rocks, is about 100-300 µm, but they can also grow to sizes of several centimeters, especially in pegmatites. Owing to their uranium and thorium content, some zircons may undergo metamictization. This partially disrupts the crystal structure and explains the ...

See also:

Zircon, Zircon - Properties, Zircon - Uses, Zircon - Zircons and the age of Earth

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Quartz is one of the world's most common crustal minerals and goes by a bewildering array of different names. The most important distinction between types of quartz is that of macrocrystalline (individual crystals visible to the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals visible only under high magnification). Chalcedony is a generic term for cryptocrystalline quartz. The cryptocrystalline varieties are either translucent or mostly opaque, while the transparent va ...

See also:

Quartz, Quartz - Varieties, Quartz - History, Quartz - Piezoelectricity

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Several studies have established preliminary links between talc and pulmonary issues [1], ovarian cancer [2], and lung cancer [3] [4]. This is a major concern considering talc's widespread commercial and household use. However, no conclusive study has yet been made to determine either the toxicity and/or carcinogenic nature of talc and the long history of safe use suggests that these concerns are unfounded. The U.S. Food and Drug Administration (FDA) considers non-asbestiform talc, that is talc which DOES NOT contain carcinogenic asbestos fibers, to be Generally Recognized As Sa ...

See also:

Talc, Talc - Safety

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Searles Lake is a huge resource of sodium and potassium minerals of the carbonate, sulfate, borate and halide classes of mineralogy. The manufacture of industrial minerals involves a complex solution mining operation in which naturally occurring brines are pumped from wells completed in several salt beds. The brine wells range in depth from near-surface to over 100 meters below the salt pan. A network of production wells, injection wells, solar ponds and piping are used in ...

See also:

Searles Lake, Searles Lake - Geology, Searles Lake - History, Searles Lake - Mineralogy, Searles Lake - Mineral List

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Cinnabar is associated with the element mercury, but contrary to popular belief, is safe to handle. This article incorporates text from the 1911 Encyclopædia Britannica, a publication in the public domain. ...

See also:

Cinnabar, Cinnabar - Of note

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Occurring as a minor accessory mineral, xenotime is found in pegmatites and other igneous rocks, as well as gneisses rich in mica and quartz. Associated minerals include biotite and other micas, chlorite group minerals, quartz, zircon, certain feldspars, analcime, anatase, brookite, rutile, siderite, and apatite. Xenotime is also known to be diagenetic: It may form as minute grains or as extremely thin (less than 10 µ) coatings on detrital zircon grains in siliciclastic sedimentary rocks. The importance of these diagenetic xenotime deposits in the radiometric dating of sedimentary rock ...

See also:

Xenotime, Xenotime - Properties, Xenotime - Occurrence

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Occurring typically in massive form, sodalite is found as vein fillings in plutonic igneous rocks such as nepheline syenites. It is associtated with other minerals typical of undersaturated environments, namely leucite, cancrinite and natrolite. Significant deposits of fine material are restricted to but a few locales: Bancroft, Ontario and Mont-Saint-Hilaire, Quebec in Canada; and Litchfield, Maine and Magnet Cove, Arkansas in the USA. Smaller deposits are found in South America (Brazil and Bolivia), Portugal, Romania, Burma and Russ ...

See also:

Sodalite, Sodalite - Properties, Sodalite - Occurrence

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In the present day, when the term "alabaster" is used without any qualification, it invariably means a fine-grained variety of gypsum. This mineral, or alabaster proper, occurs in England. However, thousands of gypsum alabaster artifacts dating to the late 4th millennium BC have been found in Tell Brak (present day Nagar), in Syria [1]. And in Mesopotamia, a gypsum alabaster sculpture, believed to represent the god Abu, dates t ...

See also:

Alabaster, Alabaster - Calcite Alabaster, Alabaster - Gypsum Alabaster

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A light, relatively hard yet fragile mineral, sodalite is named after its sodium content; in mineralogy it may be classed as a feldspathoid. Well known for its blue colour, sodalite may also be grey, yellow, green, or pink and is often mottled with white veins or patches. The more uniformly blue material is used in jewellery, where it is fashioned into cabochons and beads. Lesser material is more often seen as f ...

See also:

Sodalite, Sodalite - Properties, Sodalite - Occurrence

Read more here: » Sodalite: Encyclopedia II - Sodalite - Properties