The
geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often
biogenic (such as
calcite) or
organic compounds in the sense of chemistry (such as
mellite). Moreover, living organisms often synthesize inorganic minerals (such as
hydroxylapatite) that also occur in rocks.
The concept of mineral is distinct from
rock, which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral or may be an
aggregate of two or more different types of minerals, spacially segregated into distinct
phases.
Some natural solid substances without a definite crystalline structure, such as
opal or
obsidian, are more properly called
mineraloids. If a chemical compound occurs naturally with different crystal structures, each structure is considered a different mineral species. Thus, for example,
quartz and
stishovite are two different minerals consisting of the same compound,
silicon dioxide. (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, as well as their utilization. (Full article...)
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...)
The smallest group of particles in the 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 the principal axes, or edges, of the unit cell and the angles between them are the
lattice constants, also called lattice parameters or cell parameters. The
symmetry properties of the crystal are described by the concept of
space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups.
Hematite naturally occurs 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.
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 can
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 can also 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...)
Image 6
Cleavage, in
mineralogy and
materials science, is the tendency of
crystalline materials to
split along definite
crystallographic structural planes. These planes of relative weakness are a result of the regular locations of
atoms and
ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. If
bonds in certain directions are weaker than others, the crystal will tend to split along the weakly bonded planes. These flat breaks are termed "cleavage". The classic example of cleavage is
mica, which cleaves in a single direction along the
basal pinacoid, making the layers seem like pages in a book. In fact, mineralogists often refer to "books of mica".
Diamond and
graphite provide examples of cleavage. Each is composed solely of a single
element,
carbon. In diamond, each carbon atom is bonded to four others in a
tetrahedral pattern with short
covalent bonds. The planes of weakness (cleavage planes) in a diamond are in four directions, following the faces of the
octahedron. In graphite, carbon atoms are contained in layers in a
hexagonal pattern where the covalent bonds are shorter (and thus even stronger) than those of diamond. However, each layer is connected to the other with a longer and much weaker
van der Waals bond. This gives graphite a single direction of cleavage, parallel to the basal pinacoid. So weak is this bond that it is broken with little force, giving graphite a slippery feel as layers
shear apart. As a result, graphite makes an excellent
dry lubricant.
While all
single crystals will show some tendency to split along atomic planes in their
crystal structure, if the differences between one direction or another are not large enough, the mineral will not display cleavage.
Corundum, for example, displays no cleavage. (Full article...)
Image 7
Zeolite is a family of several
microporous, crystalline
aluminosilicate materials commonly used as commercial
adsorbents and
catalysts. They mainly consist of
silicon,
aluminium,
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+. These positive ions can be exchanged for others in a contacting
electrolyte solution. H+ exchanged zeolites are particularly useful as solid
acid catalysts.
The term was originally coined in 1756 by
SwedishmineralogistAxel 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
Greekζέω (zéō), meaning "to boil" and λίθος (líthos), meaning "stone".
Zeolites occur naturally, but are also produced industrially on a large scale. , 253 unique zeolite frameworks have been identified, and over 40 naturally occurring zeolite frameworks are known. Every new zeolite structure that is obtained is examined by the International Zeolite Association Structure Commission (IZA-SC) and receives a three-letter designation. (Full article...)
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...)
Image 9
A sample of andesite (dark groundmass) with
amygdaloidal vesicles filled with
zeolite. Diameter of view is 8 cm.
Andesite is the extrusive equivalent of
plutonicdiorite. Characteristic of
subduction zones, andesite represents the dominant rock type in
island arcs. The average composition of the
continental crust is andesitic. Along with basalts, andesites are a component of the
Martian crust.
Chalk is mined for use in industry, such as for
quicklime,
bricks and builder's
putty, and in
agriculture, for raising
pH in soils with high
acidity. It is also used for "
blackboard chalk" for writing and drawing on various types of surfaces, although these can also be manufactured from other carbonate-based minerals, or
gypsum. (Full article...)
Image 11
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.
Space groups 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.
Halite (/ˈhælaɪt,ˈheɪlaɪt/HAL-yte, HAY-lyte), commonly known as rock salt, is a type of
salt, the
mineral (natural) form of
sodium chloride (
NaCl). Halite forms
isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on inclusion of other materials,
impurities, and structural or isotopic abnormalities in the crystals. It commonly occurs with other
evaporite deposit minerals such as several of the
sulfates,
halides, and
borates. The name halite is derived from the Ancient Greek word for "salt", ἅλς (háls). (Full article...)
Before the development of
X-ray diffraction crystallography (see below), the study of
crystals was based on physical measurements of their geometry using a
goniometer. This involved measuring the angles of crystal faces relative to each other and to theoretical reference axes (crystallographic axes), and establishing the
symmetry of the crystal in question. The position in 3D space of each crystal face is plotted on a
stereographic net such as a
Wulff net or
Lambert net. The
pole to each face is plotted on the net. Each point is labelled with its
Miller index. The final plot allows the symmetry of the crystal to be established.
Crystallographic methods depend mainly on analysis of the
diffraction patterns of a sample targeted by a beam of some type.
X-rays are most commonly used; other beams used include
electrons or
neutrons. Crystallographers often explicitly state the type of beam used, as in the terms X-ray crystallography,
neutron diffraction and electron diffraction. These three types of radiation interact with the specimen in different ways.
X-rays interact with the spatial distribution of
electrons in the sample.
Neutrons are scattered by the atomic nuclei through the
strong nuclear forces, but in addition, the
magnetic moment of neutrons is non-zero. They are therefore also scattered by
magnetic fields. When neutrons are scattered from
hydrogen-containing materials, they produce diffraction patterns with high noise levels. However, the material can sometimes be treated to substitute
deuterium for hydrogen. Because of these different forms of interaction, the three types of radiation are suitable for different crystallographic studies.
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 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. Because of the remarkable
hardness of sapphires – 9 on the
Mohs scale (the third hardest mineral, after
diamond at 10 and
moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as
infraredoptical components, high-durability
windows,
wristwatch crystals and movement bearings, and very thin
electronic wafers, which are used as the
insulatingsubstrates of special-purpose
solid-state electronics such as integrated circuits and
GaN-based blue
LEDs. Sapphire is the
birthstone for September and the gem of the 45th
anniversary. A
sapphire jubilee occurs after 65 years. (Full article...)
Image 15
A lustrous crystal of zircon perched on a tan matrix of calcite from the
Gilgit District of
Pakistan
The name derives from the
Persianzargun, 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...)
Intergrowth of lustrous, cubic crystals of pyrite, with some surfaces showing characteristic striations, from Huanzala mine, Ancash, Peru. Specimen size: 7.0 × 5.0 × 2.5 cm
The
mineralpyrite (/ˈpaɪraɪt/PY-ryte), or iron pyrite, also known as fool's gold, is an
iron sulfide with the
chemical formulaFeS2 (iron (II) disulfide). Pyrite is the most abundant
sulfide mineral. Pyrite's metallic
luster and pale brass-yellow
hue give it a superficial resemblance to
gold, hence the well-known nickname of fool's gold. The color has also led to the nicknames brass, brazzle, and brazil, primarily used to refer to pyrite found in
coal.
The name pyrite is derived from the
Greekπυρίτης λίθος (pyritēs lithos), 'stone or mineral which strikes fire', in turn from πῦρ (pyr), 'fire'. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against
steel;
Pliny the Elder described one of them as being brassy, almost certainly a reference to what is now called pyrite.
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 $US4.24 billion. (Full article...)
Image 19
Magnetite from Bolivia
Magnetite is a
mineral and one of the main
iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the
oxides of iron, and is
ferrimagnetic; it is attracted to a
magnet and can be
magnetized to become a permanent magnet itself. With the exception of extremely rare
native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called
lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.
Magnetite is black or brownish-black with a metallic luster, has a
Mohs hardness of 5–6 and leaves a black
streak. Small grains of magnetite are very common in
igneous and
metamorphic rocks.
Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are
chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K; 1,063 °F). Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold.
There are many different varieties of quartz, several of which are classified as
gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of
jewelry and
hardstone carvings, especially in Europe and Asia.
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 / μεθώmetho (
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.
Like most other opaque gems, turquoise has been devalued by the introduction of treatments, imitations, and synthetics into the market. The
robin egg blue or
sky blue color of the
Persian turquoise mined near the modern city of
Nishapur,
Iran, has been used as a guiding reference for evaluating turquoise quality. (Full article...)
Galena, also called lead glance, is the natural mineral form of
lead(II) sulfide (PbS). It is the most important
ore of
lead and an important source of
silver.
Apatite (CaF) (fluorapatite) doubly-terminated crystal in calcite
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
geologistAbraham Gottlob Werner in 1786, although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German
mineralogistKarl 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. (Full article...)
In a 1948
publication on Alnö, von Eckermann correctly claimed a
magmatic origin of
carbonatite, albeit his finds were only widely accepted after the
Ol Doinyo Lengai eruption of carbonatite lava in the 1960s showed contemporary evidence on the existence of such magmas. In relation to the mid-20th century
granitization controversy von Eckermann rejected the notion that
rapakivi granites were
Jotnian sediments turned into granite. (Full article...)
Georgius Agricola (/əˈɡrɪkələ/; born Georg Bauer; 24 March 1494 – 21 November 1555) was a
GermanHumanist scholar,
mineralogist and
metallurgist. Born in the small town of
Glauchau, in the
Electorate of Saxony of the
Holy Roman Empire, he was broadly educated, but took a particular interest in the
mining and
refining of
metals. He was the first to drop the Arabic definite article al-, exclusively writing chymia and chymista in describing activity that we today would characterize as chemical or alchemical, giving
chemistry its modern name. For his groundbreaking work De Natura Fossilium published in 1546, he is generally referred to as the Father of Mineralogy and the founder of
geology as a scientific discipline.
He is well known for his pioneering work De re metallica libri XII, that was published in 1556, one year after his death. This 12-volume work is a comprehensive and systematic study, classification and methodical guide on all available factual and practical aspects, that are of concern for
mining, the mining sciences and
metallurgy, investigated and researched in its natural environment by means of direct observation. Unrivalled in its complexity and accuracy, it served as the standard reference work for two centuries. Agricola stated in the preface, that he will exclude "all those things which I have not myself seen, or have not read or heard of". He continued, "That which I have neither seen, nor carefully considered after reading or hearing of, I have not written about." (Full article...)
He studied natural sciences at the universities of
Jena and
Vienna, receiving his doctorate in 1839. In 1843 he became an associate professor at Jena, where with
Matthias Jakob Schleiden, he founded a physiological institute. At the institute he dealt with subjects that included
mineralogy,
geology,
chemistry and
physics. In 1856 he was appointed a professor of natural sciences at the University of Jena. (Full article...)
His leisure time was given up to
natural history, and especially to
mineralogy and
botany. He appears to have been the first to introduce the term "oolithus" to rocks that resemble in structure the
roe of a
fish; whence the terms "
oolite" and "oolitic". He died at Wolfenbüttel. (Full article...)
August Ferdinand von Veltheim (18 September 1741
Harbke – 2 October 1801.
Braunschweig) was a German mineralogist and geologist, and came from the aristocratic family of
Veltheim. He was known as August Ferdinand Graf von Veltheim from 1798 after acquiring the title of '
Graf'.
He attended the
Kloster Berge school (Pädagogium) near
Magdeburg between 1756 and 1758. He was introduced to the world of mining by Friedrich Anton von Heynitz, a mining official and later Minister of Industry under
Frederick the Great. In 1760 he enrolled for a course on mineralogy at the
University of Helmstedt. In 1763 he became financial advisor to the
Duke of Braunschweig, and in this capacity made numerous trips to mines and saltworks of the region in the company of his father Friedrich August von Veltheim (1709-1775). In 1766 he was promoted to Inspector of Mines in the mineral-rich mining district of the
Harz Mountains. After the death of his first son and first wife in 1779, Veltheim resigned his post and for some years withdrew from public life.[circular reference] (Full article...)
Karl von Kraatz-Koschlau was born in Reichenbach near
Stettin. He studied philosophy and sciences in
Freiburg and
Munich, where he obtained his doctorate with a dissertation on
tartaric acid and its salts (1892). Afterwards he was assigned to the
mineralogical institute in Munich. One of his scientific excursions during this time period involved geological research of the
Serra de Monchique in the
Algarve. (Full article...)
He received his education at the
University of Bonn, at the
École des Mines in
Paris and from the
University of Berlin, receiving his doctorate in 1864 with the dissertation "De rubro uranico". In 1867 he qualified as a lecturer at Berlin, and during the following year, succeeded
Lothar Meyer at the Forestry Academy in Eberswalde, where he taught classes in
chemistry,
geognosy and mineralogy. (Full article...)
Image 25
Alexandra Navrotsky with Lee Penn performing the methane mamba chemical demonstration
Alexandra Navrotsky (born 20 June 1943 in
New York City) is a physical chemist in the field of
nanogeoscience. She is an elected member of the
United States National Academy of Sciences (NAS) and the
American Philosophical Society (APS). She was a board member of the Earth Sciences and Resources division of the NAS from 1995 until 2000. In 2005, she was awarded the
Urey Medal, by the European Association of Geochemistry. In 2006, she was awarded the Harry H. Hess Medal, by the American Geophysical Union. She is currently the director of NEAT ORU (Nanomaterials in Environment, Agriculture, and Technology Organized Research Unit), a primary program in nanogeoscience. She is distinguished professor at
University of California, Davis. (Full article...)
Image 7Pink cubic
halite (NaCl; halide class) crystals on a
nahcolite matrix (NaHCO3; a carbonate, and mineral form of sodium bicarbonate, used as
baking soda). (from Mineral)
Image 8Diamond is the hardest natural material, and has a Mohs hardness of 10. (from Mineral)
Image 20Native gold. Rare specimen of stout crystals growing off of a central stalk, size 3.7 x 1.1 x 0.4 cm, from Venezuela. (from Mineral)
Image 21Mohs Scale versus Absolute Hardness (from Mineral)
Image 22Aegirine, an iron-sodium clinopyroxene, is part of the inosilicate subclass. (from Mineral)
Image 23Red cinnabar (HgS), a mercury ore, on dolomite. (from Mineral)
Image 24Epidote often has a distinctive pistachio-green colour. (from Mineral)
Image 25When minerals react, the products will sometimes assume the shape of the reagent; the product mineral is termed a pseudomorph of (or after) the reagent. Illustrated here is a pseudomorph of
kaolinite after
orthoclase. Here, the pseudomorph preserved the Carlsbad
twinning common in orthoclase. (from Mineral)
Image 26Contact twins, as seen in
spinel (from Mineral)