Portal:Minerals

Opal is a hydrated amorphous form of silica (SiO₂·nH₂O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt.

The name opal is believed to be derived from the Sanskrit word upala (उपल), which means 'jewel', and later the Greek derivative opállios (ὀπάλλιος).

There are two broad classes of opal: precious and common. Precious opal displays play-of-color (iridescence); common opal does not. Play-of-color is defined as "a pseudo chromatic optical effect resulting in flashes of colored light from certain minerals, as they are turned in white light." The internal structure of precious opal causes it to diffract light, resulting in play-of-color. Depending on the conditions in which it formed, opal may be transparent, translucent, or opaque, and the background color may be white, black, or nearly any color of the visual spectrum. Black opal is considered the rarest, while white, gray, and green opals are the most common. (Full article...)

Cinnabar (/ˈsɪnəˌbɑːr/; from Ancient Greek κιννάβαρι (kinnábari)), also called cinnabarite (/ˌsɪnəˈbɑːraɪt/) or mercurblende, is the bright scarlet to brick-red form of mercury(II) sulfide (HgS). It is the most common source ore for refining elemental mercury and is the historic source for the brilliant red or scarlet pigment termed vermilion and associated red mercury pigments.

Cinnabar generally occurs as a vein-filling mineral associated with volcanic activity and alkaline hot springs. The mineral resembles quartz in symmetry and it exhibits birefringence. Cinnabar has a mean refractive index near 3.2, a hardness between 2.0 and 2.5, and a specific gravity of approximately 8.1. The color and properties derive from a structure that is a hexagonal crystalline lattice belonging to the trigonal crystal system, crystals that sometimes exhibit twinning.

Cinnabar has been used for its color since antiquity in the Near East, including as a rouge-type cosmetic, in the New World since the Olmec culture, and in China since as early as the Yangshao culture, where it was used in coloring stoneware. In Roman times, cinnabar was highly valued as paint for walls, especially interiors, since it darkened when used outdoors due to exposure to sunlight.

Associated modern precautions for the use and handling of cinnabar arise from the toxicity of the mercury component, which was recognized as early as ancient Rome. (Full article...)

Asbestos (/æsˈbɛstəs, æz-, -tɒs/ ass-BES-təs, az-, -⁠toss) is a group of naturally occurring, fibrous silicate minerals, used for thousands of years to create flexible objects that resist fire, such as fireproof fabrics, but now known to be toxic and carcinogenic.

There are six types, all of which are composed of long and thin fibrous crystals, each fibre (particulate with length substantially greater than width) being composed of many microscopic "fibrils" that can be released into the atmosphere by abrasion and other processes. Inhalation of asbestos fibres can lead to various dangerous lung conditions, including mesothelioma, asbestosis, and lung cancer. As a result of these health effects, asbestos is considered a serious health and safety hazard.

Archaeological studies have found evidence of asbestos being used as far back as the Stone Age to strengthen ceramic pots, but large-scale mining began at the end of the 19th century when manufacturers and builders began using asbestos for its desirable physical properties. Asbestos is an excellent thermal and electrical insulator, and is highly fire-resistant, so for much of the 20th century, it was very commonly used around the world as a building material (particularly for its fire-retardant properties), until its adverse effects on human health were more widely recognized and acknowledged in the 1970s. Many buildings constructed before the 1980s contain asbestos.

The use of asbestos for construction and fireproofing has been made illegal in many countries. Despite this, around 255,000 people are thought to die each year from diseases related to asbestos exposure. In part, this is because many older buildings still contain asbestos; in addition, the consequences of exposure can take decades to arise. The latency period (from exposure until the diagnosis of negative health effects) is typically 20 years. The most common diseases associated with chronic asbestos exposure are asbestosis (scarring of the lungs due to asbestos inhalation) and mesothelioma (a type of cancer). (Full article...)

Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH⁻, F⁻ and Cl⁻ ion, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca₁₀(PO₄)₆(OH,F,Cl)₂, and the crystal unit cell formulae of the individual minerals are written as Ca₁₀(PO₄)₆(OH)₂, Ca₁₀(PO₄)₆F₂ and Ca₁₀(PO₄)₆Cl₂.

The mineral was named apatite by the German geologist Abraham Gottlob Werner in 1786, although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German mineralogist Karl Friedrich August Rammelsberg. Apatite is often mistaken for other minerals. This tendency is reflected in the mineral's name, which is derived from the Greek word ἀπατάω (apatáō), which means to deceive.

As hydroxyapatite, it forms a major part of the teeth and bones of vertebrate animals. (Full article...)

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO₄·2H₂O. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk chalk. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison.

Fine-grained white or lightly tinted forms of gypsum known as alabaster have been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England. (Full article...)

Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω (Ancient Greek) methysko / μεθώ metho (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

Amethyst, a semiprecious stone, is often used in jewelry.

It occurs mostly in association with calcite, quartz, smoky quartz, hematite, pyrite, fluorite, goethite, agate, and chalcedony. (Full article...)

Tourmaline (/ˈtʊərməlɪn, -ˌliːn/ ^ⓘ TOOR-mə-lin, -⁠leen) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.

The name is derived from the Sinhalese tōramalli (ටෝරමල්ලි), which refers to the carnelian gemstones. (Full article...)

Kaolinite (/ˈkeɪ.ələˌnaɪt, -lɪ-/ KAY-ə-lə-nyte, -⁠lih-; also called kaolin) is a clay mineral, with the chemical composition Al₂Si₂O₅(OH)₄. It is a layered silicate mineral, with one "tetrahedral" sheet of silicate tetrahedra (SiO₄) linked to one "octahedral" sheet of aluminate octahedrons (AlO₂(OH)₄) through oxygen atoms on one side, and another such sheet through hydrogen bonds on the other side.

Kaolinite is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. It has a low shrink–swell capacity and a low cation-exchange capacity (1–15 meq/100 g).

Rocks that are rich in kaolinite, and halloysite, are known as kaolin (/ˈkeɪ.əlɪn/) or china clay. In many parts of the world kaolin is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lower concentrations of iron oxide yield the white, yellow, or light orange colors of kaolin. Alternating lighter and darker layers are sometimes found, as at Providence Canyon State Park in Georgia, United States.

Kaolin is an important raw material in many industries and applications. Commercial grades of kaolin are supplied and transported as powder, lumps, semi-dried noodle or slurry. Global production of kaolin in 2021 was estimated to be 45 million tonnes, with a total market value of US $4.24 billion. (Full article...)

Zeolites are a group of several microporous, crystalline aluminosilicate minerals commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, and oxygen, and have the general formula Mⁿ⁺
_1/n(AlO
₂)⁻
(SiO
₂)
_x･yH
₂O where Mⁿ⁺
_1/n is either a metal ion or H⁺.

The term was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that rapidly heating a material, believed to have been stilbite, produced large amounts of steam from water that had been adsorbed by the material. Based on this, he called the material zeolite, from the Greek ζέω (zéō), meaning "to boil" and λίθος (líthos), meaning "stone". (Full article...)

Dolomite (/ˈdɒl.əˌmaɪt, ˈdoʊ.lə-/) is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally CaMg(CO₃)₂. The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite (see Dolomite (rock)). An alternative name sometimes used for the dolomitic rock type is dolostone. (Full article...)

Micas (/ˈmaɪkəz/ MY-kəz) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in many granites, pegmatites, and schists, and "books" (large individual crystals) of mica several feet across have been found in some pegmatites.

Micas are used in products such as drywalls, paints, and fillers, especially in parts for automobiles, roofing, and in electronics. The mineral is used in cosmetics and food to add "shimmer" or "frost". (Full article...)

In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices (an infinite array of discrete points). Space groups (symmetry groups of a configuration in space) are classified into crystal systems according to their point groups, and into lattice systems according to their Bravais lattices. Crystal systems that have space groups assigned to a common lattice system are combined into a crystal family.

The seven crystal systems are triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. Informally, two crystals are in the same crystal system if they have similar symmetries (though there are many exceptions). (Full article...)

Corundum is a crystalline form of aluminium oxide (Al₂O₃) typically containing traces of iron, titanium, vanadium, and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange.

The name "corundum" is derived from the Tamil-Dravidian word kurundam (ruby-sapphire) (appearing in Sanskrit as kuruvinda).

Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals. Emery, a variety of corundum with no value as a gemstone, is commonly used as an abrasive on sandpaper and on large tools used in machining metals, plastics, and wood. It is a black granular form of corundum, in which the mineral is intimately mixed with magnetite, hematite, or hercynite.

In addition to its hardness, corundum has a density of 4.02 g/cm³ (251 lb/cu ft), which is unusually high for a transparent mineral composed of the low-atomic mass elements aluminium and oxygen. (Full article...)

Hematite (/ˈhiːməˌtaɪt, ˈhɛmə-/), also spelled as haematite, is a common iron oxide compound with the formula Fe₂O₃ and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
₂O
₃. It has the same crystal structure as corundum (Al
₂O
₃) and ilmenite (FeTiO
₃). With this crystal structure geometry it forms a complete solid solution at temperatures above 950 °C (1,740 °F).

Hematite occurs naturally in black to steel or silver-gray, brown to reddish-brown, or red colors. It is mined as an important ore mineral of iron. It is electrically conductive. Hematite varieties include kidney ore, martite (pseudomorphs after magnetite), iron rose and specularite (specular hematite). While these forms vary, they all have a rust-red streak. Hematite is not only harder than pure iron, but also much more brittle. The term kidney ore may be broadly used to describe botryoidal, mammillary, or reniform hematite. Maghemite is a polymorph of hematite (γ-Fe
₂O
₃) with the same chemical formula, but with a spinel structure like magnetite.

Large deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that have still, standing water, or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral may precipitate in the water and collect in layers at the bottom of the lake, spring, or other standing water. Hematite can also occur in the absence of water, usually as the result of volcanic activity.

Clay-sized hematite crystals also may occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides or oxyhydroxides such as goethite, which is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils. (Full article...)

Malachite (/ˈmæl.əˌkaɪt/) is a copper carbonate hydroxide mineral, with the formula Cu₂CO₃(OH)₂. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and deep, underground spaces, where the water table and hydrothermal fluids provide the means for chemical precipitation. Individual crystals are rare, but occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur. (Full article...)

Rutile is an oxide mineral composed of titanium dioxide (TiO₂), the most common natural form of TiO₂. Rarer polymorphs of TiO₂ are known, including anatase, akaogiite, and brookite.

Rutile has one of the highest refractive indices at visible wavelengths of any known crystal and also exhibits a particularly large birefringence and high dispersion. Owing to these properties, it is useful for the manufacture of certain optical elements, especially polarization optics, for longer visible and infrared wavelengths up to about 4.5 micrometres. Natural rutile may contain up to 10% iron and significant amounts of niobium and tantalum.

Rutile derives its name from the Latin rutilus ('red'), in reference to the deep red color observed in some specimens when viewed by transmitted light. Rutile was first described in 1803 by Abraham Gottlob Werner using specimens obtained in Horcajuelo de la Sierra, Madrid (Spain), which is consequently the type locality. (Full article...)

Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, and their utilization. (Full article...)

In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.

There are three main varieties of these crystals:

• Primitive cubic (abbreviated cP and alternatively called simple cubic)
• Body-centered cubic (abbreviated cI or bcc)
• Face-centered cubic (abbreviated cF or fcc)

Note: the term fcc is often used in synonym for the cubic close-packed or ccp structure occurring in metals. However, fcc stands for a face-centered cubic Bravais lattice, which is not necessarily close-packed when a motif is set onto the lattice points. E.g. the diamond and the zincblende lattices are fcc but not close-packed.
Each is subdivided into other variants listed below. Although the unit cells in these crystals are conventionally taken to be cubes, the primitive unit cells often are not. (Full article...)

In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.

The smallest group of particles in a material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice.

The lengths of principal axes/edges, of the unit cell and angles between them are lattice constants, also called lattice parameters or cell parameters. The symmetry properties of a crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by 230 space groups.

The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency. (Full article...)

Zircon (/ˈzɜːrkɒn, -kən/) is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is ZrSiO₄. An empirical formula showing some of the range of substitution in zircon is (Zr_1–y, REE_y)(SiO₄)_1–x(OH)_4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green.

The name derives from the Persian zargun, meaning "gold-hued". This word is changed into "jargoon", a term applied to light-colored zircons. The English word "zircon" is derived from Zirkon, which is the German adaptation of this word. Yellow, orange, and red zircon is also known as "hyacinth", from the flower hyacinthus, whose name is of Ancient Greek origin. (Full article...)

Ruby is a pinkish-red to blood-red gemstone, a variety of the mineral corundum (aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires; given that the rest of the corundum species are called as such, rubies are sometimes referred to as "red sapphires".

Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the presence of chromium.

Some gemstones that are popularly or historically called rubies, such as the Black Prince's Ruby in the British Imperial State Crown, are actually spinels. These were once known as "Balas rubies".

The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red, called blood-red or pigeon blood, commands a large premium over other rubies of similar quality. After color comes clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Ruby is the traditional birthstone for July and is usually pinker than garnet, although some rhodolite garnets have a similar pinkish hue to most rubies. The world's most valuable ruby to be sold at auction is the Estrela de Fura, which sold for US$34.8 million. (Full article...)

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al₂O₃) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name sapphire is derived from the Latin word sapphirus, itself from the Greek word sappheiros (σάπφειρος), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on the locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. It occurs in association with ruby, zircon, biotite, muscovite, calcite, dravite and quartz.

Sapphire has a remarkable hardness, with a score of 9 on the Mohs scale, the third-hardest mineral after diamond at 10 and moissanite at 9.5. Non-ornamental applications include infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. (Full article...)

Garnets ( /ˈɡɑːrnɪt/) are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.

Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, defining distinct species. These species fall into two primary solid solution series: the pyralspite series (pyrope, almandine, spessartine), with the general formula [Mg,Fe,Mn]₃Al₂(SiO₄)₃; and the ugrandite series (uvarovite, grossular, andradite), with the general formula Ca₃[Cr,Al,Fe]₂(SiO₄)₃. Notable varieties of grossular include hessonite and tsavorite.

Although garnets are often associated with metamorphism, they can also occur in volcanic rocks on rare occasions. (Full article...)

Chalcopyrite (/ˌkælkəˈpaɪˌraɪt, -koʊ-/ KAL-kə-PY-ryte, -⁠koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS₂ and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.

On exposure to air, chalcopyrite tarnishes to a variety of oxides, hydroxides, and sulfates. Associated copper minerals include the sulfides bornite (Cu₅FeS₄), chalcocite (Cu₂S), covellite (CuS), digenite (Cu₉S₅); carbonates such as malachite and azurite, and rarely oxides such as cuprite (Cu₂O). It is rarely found in association with native copper. Chalcopyrite is a conductor of electricity.

Copper can be extracted from chalcopyrite ore using various methods. The two predominant methods are pyrometallurgy and hydrometallurgy, the former being the most commercially viable. (Full article...)

Crystallography is the branch of science devoted to the study of molecular and crystalline structure and properties. The word crystallography is derived from the Ancient Greek word κρύσταλλος (krústallos; "clear ice, rock-crystal"), and γράφειν (gráphein; "to write"). In July 2012, the United Nations recognised the importance of the science of crystallography by proclaiming 2014 the International Year of Crystallography.

Crystallography is a broad topic, and many of its subareas, such as X-ray crystallography, are themselves important scientific topics. Crystallography ranges from the fundamentals of crystal structure to the mathematics of crystal geometry, including those that are not periodic or quasicrystals. At the atomic scale it can involve the use of X-ray diffraction to produce experimental data that the tools of X-ray crystallography can convert into detailed positions of atoms, and sometimes electron density. At larger scales it includes experimental tools such as orientational imaging to examine the relative orientations at the grain boundary in materials. Crystallography plays a key role in many areas of biology, chemistry, and physics, as well as in emerging developments in these fields. (Full article...)

Marshall McDonald (October 18, 1835 – September 1, 1895) was an American engineer, geologist, mineralogist, pisciculturist, and fisheries scientist. McDonald served as the commissioner of the United States Commission of Fish and Fisheries from 1888 until his death in 1895. He is best known for his inventions of a number of fish hatching apparatuses and a fish ladder that enabled salmon and other migrating fish species to ascend the rapids of watercourses resulting in an increased spawning ground. McDonald's administration of the U.S. Commission of Fish and Fisheries was notably free of scandal and furthered the "protection and culture" of fish species throughout the United States.

Born in 1835 in Romney, Virginia (present-day West Virginia), McDonald was the son of Angus William McDonald, a military officer and lawyer, and his wife, Leacy Anne Naylor. From 1854 to 1855, McDonald studied natural history under Spencer Fullerton Baird at the Smithsonian Institution in Washington, D.C. He then attended the University of Virginia and Virginia Military Institute, from which he graduated in 1860. McDonald served as an assistant professor of chemistry at the institute under Stonewall Jackson and continued to teach intermittently throughout the American Civil War. (Full article...)

Waldemar Theodore Schaller (August 3, 1882 – September 28, 1967) was an American mineralogist and longtime employee of the United States Geological Survey (USGS). (Full article...)

Su Song (Chinese: 蘇頌; Pe̍h-ōe-jī: So͘ Siōng, 1020–1101), courtesy name Zirong (Chinese: 子容; Pe̍h-ōe-jī: Chú-iông), was a Chinese polymathic scientist and statesman who lived during the Song dynasty (960–1279). He excelled in numerous fields including but not limited to mathematics, astronomy, cartography, geography, metallurgy, mechanical engineering, hydraulic engineering, poetry, and statesmanship.

Su Song was the engineer for a hydro-mechanical astronomical clock tower located in Kaifeng. It employed an early escapement mechanism. The escapement mechanism of Su's clock tower was invented by the Tang dynasty Buddhist monk Yi Xing and government official Liang Lingzan in 725 AD to operate a water-powered armillary sphere, however Su's armillary sphere was the first to utilize a mechanical clock drive. Su's clock tower also featured the oldest known endless power-transmitting chain drive, called the tian ti (天梯), or "celestial ladder", as depicted in his horological treatise. The clock tower had 133 different clock jacks to indicate and sound the hours. The clock was dismantled by the invading Jurchen army in 1127 AD, and although attempts were made to reassemble it, the tower was never successfully reinstated. (Full article...)

Ignacy Domeyko or Domejko, pseudonym: Żegota (Spanish: Ignacio Domeyko, Spanish pronunciation: [iɣˈnasjo ðoˈmejko]; 31 July 1802 – 23 January 1889) was a Polish geologist, mineralogist, educator, and founder of the University of Santiago, in Chile. Domeyko spent most of his life, and died, in his adopted country, Chile.

After a youth passed in partitioned Poland, Domeyko participated in the Polish–Russian War 1830–31. Upon Russian victory, he was exiled, spending part of his life in France (where he had gone with a fellow Philomath, Polish poet Adam Mickiewicz) before eventually settling in Chile, whose citizen he became. (Full article...)

Charles-Louis-Joseph-Xavier de la Vallée Poussin (6 April 1827, Namur – 15 March 1903, Brussels) was a Belgian geologist and mineralogist. His son was the mathematician Charles Jean de la Vallée Poussin. (Full article...)

Werner Schreyer (14 November 1930 in Nuremberg; 12 February 2006 in Bochum) was a German mineralogist and experimental metamorphic petrologist. Schreyer completed his undergraduate work in geology and petrology at the University of Erlangen-Nuremberg, obtained his doctorate from the University of Munich in 1957, and in 1966 received his Habilitation from the University of Kiel. He was a professor at Ruhr University Bochum from 1966 to 1996. In 2002 Schreyer became the first German to be awarded the Mineralogical Society of America's highest honor, the Roebling Medal. Schreyer was a leading expert on phase relations in the MgO–Al₂O₃–SiO₂–H₂O (MASH) system, specializing in cordierite and minerals with equivalent chemical compositions, and high pressure and ultra high-pressure metamorphic mineral assemblages.

The mineral Schreyerite (V2Ti3O9) was named after Schreyer. (Full article...)

Charles Louis Christ (March 12, 1916 – June 29, 1980) was an American scientist, geochemist and mineralogist. (Full article...)

John Walker FRSE (1731–1803) was a Scottish minister and natural historian. He was Regius professor of natural history at the University of Edinburgh from 1779 to 1803. He was joint founder of the Royal Society of Edinburgh in 1783 and moderator of the General Assembly of the Church of Scotland in 1790. (Full article...)

Johann Carl Gehler (17 May 1732 – 6 May 1796) was a German physician, mineralogist, and anatomist.

Born 17 May 1732 in Görlitz, Gehler studied medicine from 1751 to 1758 at the University of Leipzig, where he was a pupil of physician and botanist Christian Gottlieb Ludwig. While a student at Leipzig, he furthered his interest in natural sciences, publishing the mineralogical treatise, De characteribus fossilium externis (1757), as a result. Following graduation, he continued his education by studying mineralogy in Freiberg and obstetrics in Strasbourg as a student of Johann Jakob Fried (1689–1769). (Full article...)

Norman Levi Bowen FRS (June 21, 1887 – September 11, 1956) was a Canadian geologist. Bowen "revolutionized experimental petrology and our understanding of mineral crystallization". Beginning geology students are familiar with Bowen's reaction series depicting how different minerals crystallize under varying pressures and temperatures." (Full article...)

Vasily Mikhailovich Severgin (Russian: Василий Михайлович Севергин; 19 September 1765 – 29 November 1826) was a Russian academician, chemist, mineralogist, and geologist. For three decades, he was the only academician elected to the Geological Society of London. He has been described as being among the most influential pioneers of geology in Russia. (Full article...)

Waldemar Christofer Brøgger ForMemRS FRSE (10 November 1851 – 17 February 1940) was a Norwegian geologist and mineralogist. His research on Permian igneous rocks (286 to 245 million years ago) of the Oslo district greatly advanced petrologic theory on the formation of rocks. (Full article...)

William Sefton Fyfe, CC FRSC FRS FRSNZ (4 June 1927 – 11 November 2013) was a New Zealand geologist and Professor Emeritus in the department of Earth Sciences at the University of Western Ontario. He is widely considered among the world's most eminent geochemists. (Full article...)

André-Jean-François-Marie Brochant de Villiers (6 August 1772 – 16 May 1840) was a French mineralogist and geologist. (Full article...)

Frank Christopher Hawthorne CC FRSC (born 8 January 1946) is an English-born Canadian mineralogist, crystallographer and spectroscopist. He works at the University of Manitoba and is currently distinguished professor emeritus. By combining graph theory, bond-valence theory and the moments approach to the electronic energy density of solids he has developed bond topology as a rigorous approach to understanding the atomic arrangements, chemical compositions and paragenesis of complex oxide and oxysalt minerals. (Full article...)

Quintino Sella (Italian pronunciation: [kwinˈtino ˈsɛlla]; 7 July 1827 – 14 March 1884) was an Italian politician, economist and mountaineer. (Full article...)

William Phillips FGS FRS (10 May 1775 – 2 April 1828) was an English mineralogist and geologist. (Full article...)

Ignaz Edler von Born, also known as Ignatius von Born (Hungarian: Born Ignác, Romanian: Ignațiu von Born, Czech: Ignác Born) (26 December 1742 in Alba Iulia, Grand Principality of Transylvania, Habsburg monarchy – 24 July 1791 in Vienna), was a mineralogist and metallurgist. He was a prominent freemason, being head of Vienna's lodge and an influential anti-clerical writer. He was the leading scientist in the Holy Roman Empire during the 1770s in the Age of Enlightenment.

His interests include mining, mineralogy, palaeontology, chemistry, metallurgy and malacology. (Full article...)

Paul Niggli (26 June 1888 – 13 January 1953) was a Swiss crystallographer, mineralogist, and petrologist who was a leader in the field of X-ray crystallography. (Full article...)

Wolfgang Xavier Franz Ritter von Kobell (19 July 1803 – 11 November 1882) was a German mineralogist and writer of short stories and poems in Bavarian dialect. (Full article...)

Jean-André Mongez (21 November 1750 – May 1788) was a French priest and mineralogist. He is presumed to have died at Vanikoro, on the La Pérouse expedition. (Full article...)

Abraham Gottlob Werner (German: [ˈaːbʁaham ˈɡɔtloːp ˈvɛʁnɐ]; 25 September 1749 – 30 June 1817) was a German geologist who set out an early theory about the stratification of the Earth's crust and propounded a history of the Earth that came to be known as Neptunism. While most tenets of Neptunism were eventually set aside, Werner is remembered for his demonstration of chronological succession in rocks; for the zeal with which he infused his pupils; and for the impulse he thereby gave to the study of geology. He has been called the "father of German geology". (Full article...)

Gregori Aminoff (8 February 1883 – 11 February 1947) was a Swedish mineralogist, artist, and a member of the Aminoff family. During his career, Aminoff introduced X-ray diffraction and electron diffraction to the Swedish scientific community and was a pioneer in crystallography in Sweden. (Full article...)

Pierre Bernard Palassou (9 June 1745, Oloron-Sainte-Marie – 9 April 1830, Ogenne-Camptort) was a French naturalist known for pioneer geological and mineralogical studies of the Pyrénées.

He was a correspondent member of the Académie des sciences (1816–1830) and an honorary member of the Société linnéenne de Paris (1821). His name is associated with the "Poudingues de Palassou", which are enormous beds of conglomerate rock found in the Pyrénées. In 1784 he described Quercus palensis (Pyrenean oak) of the botanical family Fagaceae, (synonym Quercus pyrenaica Willd.). (Full article...)

Peter John Wyllie (born 8 February 1930, in London, England) is a British petrologist and academic.

He was Professor of Geology at the California Institute of Technology from 1983 until his retirement in 1999. Prior to this, he held positions at the University of St Andrews (1955–56), Pennsylvania State University (1958–59 and 1961–66), the University of Leeds (1959–61), and the University of Chicago (1965–83). He is well known for his many contributions to the understanding of magmatism, particularly through his work on the experimental petrology of magmas and volatiles. In the early 1970s, Wyllie wrote two widely used textbooks; The Dynamic Earth (1971) and The Way the Earth Works (1976) which integrated the new understanding of magmatism and plate tectonics. He is also famous for his contributions to the coverage of earth sciences in the Encyclopædia Britannica, particularly his outline of the field in Part Two of the Propædia. Wyllie was President of the International Union of Geodesy and Geophysics (IUGG) from 1995 to 1999. (Full article...)