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60-752: Christian Samuel Weiss (26 February 1780 – 1 October 1856) was a German mineralogist born in Leipzig . Following graduation, he worked as a physics instructor in Leipzig from 1803 until 1808. and in the meantime, conducted geological studies of mountain formations in Tyrol , Switzerland and France (1806–08). In 1810 he became a professor of mineralogy at the University of Berlin , where in 1818/19 and 1832/33, he served as university rector . He died near Eger in Bohemia . Weiss

120-444: A ( polarizer ) below the sample and an analyzer above it, polarized perpendicular to each other. Light passes successively through the polarizer, the sample and the analyzer. If there is no sample, the analyzer blocks all the light from the polarizer. However, an anisotropic sample will generally change the polarization so some of the light can pass through. Thin sections and powders can be used as samples. When an isotropic crystal

180-548: A polarizing microscope . James D. Dana published his first edition of A System of Mineralogy in 1837, and in a later edition introduced a chemical classification that is still the standard. X-ray diffraction was demonstrated by Max von Laue in 1912, and developed into a tool for analyzing the crystal structure of minerals by the father/son team of William Henry Bragg and William Lawrence Bragg . More recently, driven by advances in experimental technique (such as neutron diffraction ) and available computational power,

240-464: A sclerometer ; compared to the absolute scale, the Mohs scale is nonlinear. Tenacity refers to the way a mineral behaves, when it is broken, crushed, bent or torn. A mineral can be brittle , malleable , sectile , ductile , flexible or elastic . An important influence on tenacity is the type of chemical bond ( e.g., ionic or metallic ). Of the other measures of mechanical cohesion, cleavage

300-411: A crystal and its thermal motions can be determined with greater precision by neutron diffraction. The structures of metal hydride complexes , e.g., Mg 2 FeH 6 have been assessed by neutron diffraction. The neutron scattering lengths b H = −3.7406(11) fm and b D = 6.671(4) fm, for H and D respectively, have opposite sign, which allows the technique to distinguish them. In fact there

360-441: A diffraction experiment. Impinging on a crystalline sample, it will scatter under a limited number of well-defined angles, according to the same Bragg's law that describes X-ray diffraction. Neutrons and X-rays interact with matter differently. X-rays interact primarily with the electron cloud surrounding each atom. The contribution to the diffracted x-ray intensity is therefore larger for atoms with larger atomic number (Z) . On

420-474: A diffraction pattern that provides information of the structure of the material. The technique is similar to X-ray diffraction but due to their different scattering properties, neutrons and X-rays provide complementary information: X-Rays are suited for superficial analysis, strong x-rays from synchrotron radiation are suited for shallow depths or thin specimens, while neutrons having high penetration depth are suited for bulk samples. The technique requires

480-422: A higher cross section for neutron interaction than higher atomic weight materials. One major advantage of neutron diffraction over X-ray diffraction is that the latter is rather insensitive to the presence of hydrogen (H) in a structure, whereas the nuclei H and H (i.e. Deuterium , D) are strong scatterers for neutrons. The greater scattering power of protons and deuterons means that the position of hydrogen in

540-400: A map of the lattice constant through the metal can be derived. This can easily be converted to the stress field experienced by the material. This has been used to analyse stresses in aerospace and automotive components to give just two examples. The high penetration depth permits measuring residual stresses in bulk components as crankshafts, pistons, rails, gears. This technique has led to

600-449: A much smaller sample) has essentially the same relationship. This implies that, given the chemical composition of the planet, one could predict the more common minerals. However, the distribution has a long tail , with 34% of the minerals having been found at only one or two locations. The model predicts that thousands more mineral species may await discovery or have formed and then been lost to erosion, burial or other processes. This implies

660-453: A polarizing microscope to observe. When light passes from air or a vacuum into a transparent crystal, some of it is reflected at the surface and some refracted . The latter is a bending of the light path that occurs because the speed of light changes as it goes into the crystal; Snell's law relates the bending angle to the Refractive index , the ratio of speed in a vacuum to speed in

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720-836: A role of chance in the formation of rare minerals occur. In another use of big data sets, network theory was applied to a dataset of carbon minerals, revealing new patterns in their diversity and distribution. The analysis can show which minerals tend to coexist and what conditions (geological, physical, chemical and biological) are associated with them. This information can be used to predict where to look for new deposits and even new mineral species. Minerals are essential to various needs within human society, such as minerals used as ores for essential components of metal products used in various commodities and machinery , essential components to building materials such as limestone , marble , granite , gravel , glass , plaster , cement , etc. Minerals are also used in fertilizers to enrich

780-457: A source of neutrons. Neutrons are usually produced in a nuclear reactor or spallation source . At a research reactor , other components are needed, including a crystal monochromator (in the case of thermal neutrons), as well as filters to select the desired neutron wavelength. Some parts of the setup may also be movable. For the long-wavelength neutrons, crystals cannot be used and gratings are used instead as diffractive optical components. At

840-413: A spallation source, the time of flight technique is used to sort the energies of the incident neutrons (higher energy neutrons are faster), so no monochromator is needed, but rather a series of aperture elements synchronized to filter neutron pulses with the desired wavelength. The technique is most commonly performed as powder diffraction , which only requires a polycrystalline powder. Single crystal work

900-444: Is a particular isotope ratio for which the contribution of the element would cancel, this is called null-scattering. It is undesirable to work with the relatively high concentration of H in a sample. The scattering intensity by H-nuclei has a large inelastic component, which creates a large continuous background that is more or less independent of scattering angle. The elastic pattern typically consists of sharp Bragg reflections if

960-408: Is also possible, but the crystals must be much larger than those that are used in single-crystal X-ray crystallography . It is common to use crystals that are about 1 mm . The technique also requires a device that can detect the neutrons after they have been scattered. Summarizing, the main disadvantage to neutron diffraction is the requirement for a nuclear reactor. For single crystal work,

1020-407: Is comparable with the wavelength . If the wavelength of a quantum particle is short enough, atoms or their nuclei can serve as diffraction obstacles. When a beam of neutrons emanating from a reactor is slowed and selected properly by their speed, their wavelength lies near one angstrom (0.1 nanometer ), the typical separation between atoms in a solid material. Such a beam can then be used to perform

1080-419: Is credited for creating parameters of modern crystallography , and was instrumental in making it a branch of mathematical science. He stressed the significance of direction in crystals, considering crystallographic axes to be a possible basis for classification of crystals. He is credited for introducing the categorization schema of crystal systems , and has a basic law of crystallography named after him called

1140-526: Is determined by comparison with other minerals. In the Mohs scale , a standard set of minerals are numbered in order of increasing hardness from 1 (talc) to 10 (diamond). A harder mineral will scratch a softer, so an unknown mineral can be placed in this scale, by which minerals; it scratches and which scratch it. A few minerals such as calcite and kyanite have a hardness that depends significantly on direction. Hardness can also be measured on an absolute scale using

1200-498: Is inexpensive and particularly interesting, because it plays an exceptionally large role in biochemical structures and is difficult to study structurally in other ways. Neutron was discovered around early 1930s, and diffraction was first observed in 1936 by two groups, von Halban and Preiswerk and by Mitchell and Powers. In 1944, Ernest O. Wollan , with a background in X-ray scattering from his PhD work under Arthur Compton , recognized

1260-454: Is similar to wet chemistry in that the sample must still be dissolved, but it is much faster and cheaper. The solution is vaporized and its absorption spectrum is measured in the visible and ultraviolet range. Other techniques are X-ray fluorescence , electron microprobe analysis atom probe tomography and optical emission spectrography . In addition to macroscopic properties such as colour or lustre, minerals have properties that require

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1320-399: Is the arrangement of atoms in a crystal. It is represented by a lattice of points which repeats a basic pattern, called a unit cell , in three dimensions. The lattice can be characterized by its symmetries and by the dimensions of the unit cell. These dimensions are represented by three Miller indices . The lattice remains unchanged by certain symmetry operations about any given point in

1380-573: Is the identification and classification of minerals by their properties. Historically, mineralogy was heavily concerned with taxonomy of the rock-forming minerals. In 1959, the International Mineralogical Association formed the Commission of New Minerals and Mineral Names to rationalize the nomenclature and regulate the introduction of new names. In July 2006, it was merged with the Commission on Classification of Minerals to form

1440-432: Is the tendency to break along certain crystallographic planes. It is described by the quality ( e.g. , perfect or fair) and the orientation of the plane in crystallographic nomenclature. Parting is the tendency to break along planes of weakness due to pressure, twinning or exsolution . Where these two kinds of break do not occur, fracture is a less orderly form that may be conchoidal (having smooth curves resembling

1500-481: Is viewed, it appears dark because it does not change the polarization of the light. However, when it is immersed in a calibrated liquid with a lower index of refraction and the microscope is thrown out of focus, a bright line called a Becke line appears around the perimeter of the crystal. By observing the presence or absence of such lines in liquids with different indices, the index of the crystal can be estimated, usually to within ± 0.003 . Systematic mineralogy

1560-457: The crowd-sourced site Mindat.org , which has over 690,000 mineral-locality pairs, with the official IMA list of approved minerals and age data from geological publications. This database makes it possible to apply statistics to answer new questions, an approach that has been called mineral ecology . One such question is how much of mineral evolution is deterministic and how much the result of chance . Some factors are deterministic, such as

1620-476: The microscopic study of rock sections with the invention of the microscope in the 17th century. Nicholas Steno first observed the law of constancy of interfacial angles (also known as the first law of crystallography) in quartz crystals in 1669. This was later generalized and established experimentally by Jean-Baptiste L. Romé de l'Islee in 1783. René Just Haüy , the "father of modern crystallography", showed that crystals are periodic and established that

1680-585: The static structure factor of gases , liquids or amorphous solids . Most experiments, however, aim at the structure of crystalline solids, making neutron diffraction an important tool of crystallography . Neutron diffraction is closely related to X-ray powder diffraction . In fact, the single crystal version of the technique is less commonly used because currently available neutron sources require relatively large samples and large single crystals are hard or impossible to come by for most materials. Future developments, however, may well change this picture. Because

1740-776: The "Weiss zone law". Mineralogist Early writing on mineralogy, especially on gemstones , comes from ancient Babylonia , the ancient Greco-Roman world, ancient and medieval China , and Sanskrit texts from ancient India and the ancient Islamic world. Books on the subject included the Natural History of Pliny the Elder , which not only described many different minerals but also explained many of their properties, and Kitab al Jawahir (Book of Precious Stones) by Persian scientist Al-Biruni . The German Renaissance specialist Georgius Agricola wrote works such as De re metallica ( On Metals , 1556) and De Natura Fossilium ( On

1800-556: The Commission on New Minerals, Nomenclature, and Classification. There are over 6,000 named and unnamed minerals, and about 100 are discovered each year. The Manual of Mineralogy places minerals in the following classes: native elements , sulfides , sulfosalts , oxides and hydroxides , halides , carbonates, nitrates and borates , sulfates, chromates, molybdates and tungstates , phosphates, arsenates and vanadates , and silicates . The environments of mineral formation and growth are highly varied, ranging from slow crystallization at

1860-453: The Nature of Rocks , 1546) which began the scientific approach to the subject. Systematic scientific studies of minerals and rocks developed in post- Renaissance Europe. The modern study of mineralogy was founded on the principles of crystallography (the origins of geometric crystallography, itself, can be traced back to the mineralogy practiced in the eighteenth and nineteenth centuries) and to

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1920-399: The atomic number. An element like vanadium strongly scatters X-rays, but its nuclei hardly scatters neutrons, which is why it is often used as a container material. Non-magnetic neutron diffraction is directly sensitive to the positions of the nuclei of the atoms. The nuclei of atoms, from which neutrons scatter, are tiny. Furthermore, there is no need for an atomic form factor to describe

1980-420: The atomic positions in the structure can be determined with high precision. On the other hand, Fourier maps (and to a lesser extent difference Fourier maps ) derived from neutron data suffer from series termination errors, sometimes so much that the results are meaningless. Although neutrons are uncharged, they carry a magnetic moment , and therefore interact with magnetic moments, including those arising from

2040-465: The basic principles of the technique, and applied it successfully to many different materials, addressing problems like the structure of ice and the microscopic arrangements of magnetic moments in materials. For this achievement, Shull was awarded one half of the 1994 Nobel Prize in Physics . (Wollan died in 1984). (The other half of the 1994 Nobel Prize for Physics went to Bert Brockhouse for development of

2100-450: The chemical nature of a mineral and conditions for its stability ; but mineralogy can also be affected by the processes that determine a planet's composition. In a 2015 paper, Robert Hazen and others analyzed the number of minerals involving each element as a function of its abundance. They found that Earth, with over 4800 known minerals and 72 elements, has a power law relationship. The Moon, with only 63 minerals and 24 elements (based on

2160-721: The connection between atomic-scale phenomena and macroscopic properties, the mineral sciences (as they are now commonly known) display perhaps more of an overlap with materials science than any other discipline. An initial step in identifying a mineral is to examine its physical properties, many of which can be measured on a hand sample. These can be classified into density (often given as specific gravity ); measures of mechanical cohesion ( hardness , tenacity , cleavage , fracture , parting ); macroscopic visual properties ( luster , color, streak , luminescence , diaphaneity ); magnetic and electric properties; radioactivity and solubility in hydrogen chloride ( H Cl ). Hardness

2220-562: The crystal structures of minerals. X-rays have wavelengths that are the same order of magnitude as the distances between atoms. Diffraction , the constructive and destructive interference between waves scattered at different atoms, leads to distinctive patterns of high and low intensity that depend on the geometry of the crystal. In a sample that is ground to a powder, the X-rays sample a random distribution of all crystal orientations. Powder diffraction can distinguish between minerals that may appear

2280-416: The crystal. Crystals whose point symmetry group falls in the cubic system are isotropic : the index does not depend on direction. All other crystals are anisotropic : light passing through them is broken up into two plane polarized rays that travel at different speeds and refract at different angles. A polarizing microscope is similar to an ordinary microscope, but it has two plane-polarized filters,

2340-530: The data is typically a 1D powder diffractogram they are usually processed using Rietveld refinement . In fact the latter found its origin in neutron diffraction (at Petten in the Netherlands) and was later extended for use in X-ray diffraction. One practical application of elastic neutron scattering/diffraction is that the lattice constant of metals and other crystalline materials can be very accurately measured. Together with an accurately aligned micropositioner

2400-501: The development of dedicated stress diffractometers, such as the ENGIN-X instrument at the ISIS neutron source . Neutron diffraction can also be employed to give insight into the 3D structure any material that diffracts. Another use is for the determination of the solvation number of ion pairs in electrolytes solutions. The magnetic scattering effect has been used since the establishment of

2460-424: The electron cloud around an atom. Neutron diffraction can therefore reveal the microscopic magnetic structure of a material. Magnetic scattering does require an atomic form factor as it is caused by the much larger electron cloud around the tiny nucleus. The intensity of the magnetic contribution to the diffraction peaks will therefore decrease towards higher angles. Neutron diffraction can be used to determine

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2520-443: The existence of the antiferromagnetic arrangement of magnetic dipoles in a material structure. Now, neutron diffraction continues to be used to characterize newly developed magnetic materials. Neutron diffraction can be used to establish the structure of low atomic number materials like proteins and surfactants much more easily with lower flux than at a synchrotron radiation source. This is because some low atomic number materials have

2580-476: The field has made great advances in the understanding of the relationship between the atomic-scale structure of minerals and their function; in nature, prominent examples would be accurate measurement and prediction of the elastic properties of minerals, which has led to new insight into seismological behaviour of rocks and depth-related discontinuities in seismograms of the Earth's mantle . To this end, in their focus on

2640-597: The growth of agricultural crops. Mineral collecting is also a recreational study and collection hobby , with clubs and societies representing the field. Museums, such as the Smithsonian National Museum of Natural History Hall of Geology, Gems, and Minerals , the Natural History Museum of Los Angeles County , the Carnegie Museum of Natural History , the Natural History Museum, London , and

2700-690: The high temperatures and pressures of igneous melts deep within the Earth's crust to the low temperature precipitation from a saline brine at the Earth's surface. Various possible methods of formation include: Biomineralogy is a cross-over field between mineralogy, paleontology and biology . It is the study of how plants and animals stabilize minerals under biological control, and the sequencing of mineral replacement of those minerals after deposition. It uses techniques from chemical mineralogy, especially isotopic studies, to determine such things as growth forms in living plants and animals as well as things like

2760-541: The inelastic scattering technique at the Chalk River facility of AECL . This also involved the invention of the triple axis spectrometer). The delay between the achieved work (1946) and the Nobel Prize awarded to Brockhouse and Shull (1994) brings them close to the delay between the invention by Ernst Ruska of the electron microscope (1933) - also in the field of particle optics - and his own Nobel prize (1986). This in turn

2820-529: The interior of a shell), fibrous , splintery , hackly (jagged with sharp edges), or uneven . If the mineral is well crystallized, it will also have a distinctive crystal habit (for example, hexagonal, columnar, botryoidal ) that reflects the crystal structure or internal arrangement of atoms. It is also affected by crystal defects and twinning . Many crystals are polymorphic , having more than one possible crystal structure depending on factors such as pressure and temperature. The crystal structure

2880-422: The latter of which has enabled extremely accurate atomic-scale simulations of the behaviour of crystals, the science has branched out to consider more general problems in the fields of inorganic chemistry and solid-state physics . It, however, retains a focus on the crystal structures commonly encountered in rock-forming minerals (such as the perovskites , clay minerals and framework silicates ). In particular,

2940-540: The lattice: reflection , rotation , inversion , and rotary inversion , a combination of rotation and reflection. Together, they make up a mathematical object called a crystallographic point group or crystal class . There are 32 possible crystal classes. In addition, there are operations that displace all the points: translation , screw axis , and glide plane . In combination with the point symmetries, they form 230 possible space groups . Most geology departments have X-ray powder diffraction equipment to analyze

3000-416: The neutron diffraction technique to quantify magnetic moments in materials, and study the magnetic dipole orientation and structure. One of the earliest applications of neutron diffraction was in the study of magnetic dipole orientations in antiferromagnetic transition metal oxides such as manganese, iron, nickel, and cobalt oxides. These experiments, first performed by Clifford Shull, were the first to show

3060-586: The orientations of crystal faces can be expressed in terms of rational numbers, as later encoded in the Miller indices. In 1814, Jöns Jacob Berzelius introduced a classification of minerals based on their chemistry rather than their crystal structure. William Nicol developed the Nicol prism , which polarizes light, in 1827–1828 while studying fossilized wood; Henry Clifton Sorby showed that thin sections of minerals could be identified by their optical properties using

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3120-440: The original mineral content of fossils. A new approach to mineralogy called mineral evolution explores the co-evolution of the geosphere and biosphere, including the role of minerals in the origin of life and processes as mineral-catalyzed organic synthesis and the selective adsorption of organic molecules on mineral surfaces. In 2011, several researchers began to develop a Mineral Evolution Database. This database integrates

3180-436: The other hand, neutrons interact directly with the nucleus of the atom, and the contribution to the diffracted intensity depends on each isotope ; for example, regular hydrogen and deuterium contribute differently. It is also often the case that light (low Z) atoms contribute strongly to the diffracted intensity, even in the presence of large Z atoms. The scattering length varies from isotope to isotope rather than linearly with

3240-496: The potential for applying thermal neutrons from the newly operational X-10 nuclear reactor to crystallography . Joined by Clifford G. Shull they developed neutron diffraction throughout the 1940s. The first neutron diffraction experiments were carried out in 1945 by Ernest O. Wollan using the Graphite Reactor at Oak Ridge . He was joined shortly thereafter (June 1946) by Clifford Shull , and together they established

3300-465: The private Mim Mineral Museum in Beirut , Lebanon , have popular collections of mineral specimens on permanent display. Neutron diffraction Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to obtain

3360-702: The same in a hand sample, for example quartz and its polymorphs tridymite and cristobalite . Isomorphous minerals of different compositions have similar powder diffraction patterns, the main difference being in spacing and intensity of lines. For example, the Na Cl ( halite ) crystal structure is space group Fm3m ; this structure is shared by sylvite ( K Cl ), periclase ( Mg O ), bunsenite ( Ni O ), galena ( Pb S ), alabandite ( Mn S ), chlorargyrite ( Ag Cl ), and osbornite ( Ti N ). A few minerals are chemical elements , including sulfur , copper , silver , and gold , but

3420-429: The sample is crystalline. They tend to drown in the inelastic background. This is even more serious when the technique is used for the study of liquid structure. Nevertheless, by preparing samples with different isotope ratios, it is possible to vary the scattering contrast enough to highlight one element in an otherwise complicated structure. The variation of other elements is possible but usually rather expensive. Hydrogen

3480-499: The shape of the electron cloud of the atom and the scattering power of an atom does not fall off with the scattering angle as it does for X-rays. Diffractograms therefore can show strong, well-defined diffraction peaks even at high angles, particularly if the experiment is done at low temperatures. Many neutron sources are equipped with liquid helium cooling systems that allow data collection at temperatures down to 4.2 K. The superb high angle (i.e. high resolution ) information means that

3540-473: The technique requires relatively large crystals, which are usually challenging to grow. The advantages to the technique are many - sensitivity to light atoms, ability to distinguish isotopes, absence of radiation damage, as well as a penetration depth of several cm Like all quantum particles , neutrons can exhibit wave phenomena typically associated with light or sound. Diffraction is one of these phenomena; it occurs when waves encounter obstacles whose size

3600-425: The vast majority are compounds . The classical method for identifying composition is wet chemical analysis , which involves dissolving a mineral in an acid such as hydrochloric acid (HCl). The elements in solution are then identified using colorimetry , volumetric analysis or gravimetric analysis . Since 1960, most chemistry analysis is done using instruments. One of these, atomic absorption spectroscopy ,

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