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.
111-728: 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
222-442: 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
333-538: 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,
444-460: 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
555-494: A variable void fraction which depends on how the material is agitated or poured. It might be loose or compact, with more or less air space depending on handling. In practice, the void fraction is not necessarily air, or even gaseous. In the case of sand, it could be water, which can be advantageous for measurement as the void fraction for sand saturated in water—once any air bubbles are thoroughly driven out—is potentially more consistent than dry sand measured with an air void. In
666-462: 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
777-442: A cubic crystal system, are often found as octahedrons . Gemstones are classified into different groups , species , and varieties . For example, ruby is the red variety of the species corundum , while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow), and morganite (pink), which are all varieties of
888-504: A diamond. With modification, these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weights depending upon whether they are applied to colored gemstones or to colorless diamonds. In diamonds, the cut is the primary determinant of value, followed by clarity and color. An ideally cut diamond will sparkle, to break down light into its constituent rainbow colors (dispersion), chop it up into bright little pieces (scintillation), and deliver it to
999-447: A gemstone is a natural stone or synthetic, the chemical, physical, and optical characteristics are the same: They are composed of the same mineral and are colored by the same trace materials, have the same hardness and density and strength , and show the same color spectrum , refractive index , and birefringence (if any). Lab-created stones tend to have a more vivid color since impurities common in natural stones are not present in
1110-433: A more desirable blue / purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity. When jewelry containing diamonds is heated for repairs, the diamond should be protected with boric acid ; otherwise, the diamond, which is pure carbon, could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies
1221-449: 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
SECTION 10
#17328486043791332-483: A number of inclusions), cut, unusual optical phenomena within the stone such as color zoning (the uneven distribution of coloring within a gem) and asteria (star effects). Apart from the more generic and commonly used gemstones such as from diamonds , rubies , sapphires , and emeralds , pearls and opal have also been defined as precious in the jewellery trade. Up to the discoveries of bulk amethyst in Brazil in
1443-453: 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
1554-626: A result of this is the exploitation of natural resources and labor within gemstone mining operations. Many mines, particularly in developing countries, face challenges such as inadequate safety measures, low wages, and poor working conditions. Miners , often from disadvantaged backgrounds, endure hazardous working conditions and receive meager wages, contributing to cycles of poverty and exploitation. Gemstone mining operations are frequently conducted in remote or underdeveloped areas, lacking proper infrastructure and access to essential services such as healthcare and education. This further contributes to
1665-828: 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
1776-942: A solution sums to density of the solution, ρ = ∑ i ρ i . {\displaystyle \rho =\sum _{i}\rho _{i}.} Expressed as a function of the densities of pure components of the mixture and their volume participation , it allows the determination of excess molar volumes : ρ = ∑ i ρ i V i V = ∑ i ρ i φ i = ∑ i ρ i V i ∑ i V i + ∑ i V E i , {\displaystyle \rho =\sum _{i}\rho _{i}{\frac {V_{i}}{V}}\,=\sum _{i}\rho _{i}\varphi _{i}=\sum _{i}\rho _{i}{\frac {V_{i}}{\sum _{i}V_{i}+\sum _{i}{V^{E}}_{i}}},} provided that there
1887-610: A stone is untreated, while another lab might conclude that it is heat-treated. To minimize such differences, seven of the most respected labs, AGTA-GTL (New York), CISGEM (Milano), GAAJ-ZENHOKYO (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), for the standardization of wording reports, promotion of certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to determine, due to
1998-455: A substance does not increase its density; rather it increases its mass. Other conceptually comparable quantities or ratios include specific density , relative density (specific gravity) , and specific weight . The understanding that different materials have different densities, and of a relationship between density, floating, and sinking must date to prehistoric times. Much later it was put in writing. Aristotle , for example, wrote: There
2109-399: A temperature increase on the order of thousands of degrees Celsius . In contrast, the density of gases is strongly affected by pressure. The density of an ideal gas is ρ = M P R T , {\displaystyle \rho ={\frac {MP}{RT}},} where M is the molar mass , P is the pressure, R is the universal gas constant , and T
2220-448: Is hardstone . Use of the terms 'precious' and 'semi-precious' in a commercial context is, arguably, misleading in that it suggests certain stones are more valuable than others when this is not reflected in the actual market value, although it would generally be correct if referring to desirability. In modern times gemstones are identified by gemologists , who describe gems and their characteristics using technical terminology specific to
2331-411: Is mass divided by volume . As there are many units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per cubic metre (kg/m ) and the cgs unit of gram per cubic centimetre (g/cm ) are probably the most commonly used units for density. One g/cm is equal to 1000 kg/m . One cubic centimetre (abbreviation cc)
SECTION 20
#17328486043792442-434: Is a common practice. Most citrine is made by heating amethyst , and partial heating with a strong gradient results in " ametrine " – a stone partly amethyst and partly citrine. Aquamarine is often heated to remove yellow tones, or to change green colors into the more desirable blue, or enhance its existing blue color to a deeper blue. Nearly all tanzanite is heated at low temperatures to remove brown undertones and give
2553-500: Is a recognized grading of the gem's luster, transparency, or "brilliance". Very transparent gems are considered " first water ", while "second" or "third water" gems are those of a lesser transparency. Additionally, material or flaws within a stone may be present as inclusions . Gemstones have no universally accepted grading system. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in
2664-522: Is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner. Fracture filling has been in use with different gemstones such as diamonds, emeralds, and sapphires. In 2006 "glass-filled rubies" received publicity. Rubies over 10 carats (2 g) with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect. Another treatment method that
2775-440: Is commonly used to treat gemstones is bleaching. This method uses a chemical in order to reduce the colour of the gem. After bleaching, a combination treatment can be done by dying the gemstone once the unwanted colours are removed. Hydrogen peroxide is the most commonly used product used to alter gemstones and have notably been used to treat jade and pearls. The treatment of bleaching can also be followed by impregnation, which allows
2886-511: Is considered to be one of the important gemstones after rubies, emeralds, and sapphires according to Gübelin Gemlab. Even though it is a tourmaline, Paraiba Tourmaline is one of the most expensive gemstones. There are a number of laboratories which grade and provide reports on gemstones. Each laboratory has its own methodology to evaluate gemstones. A stone can be called "pink" by one lab while another lab calls it "padparadscha". One lab can conclude
2997-524: 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
3108-501: Is emerald (green). Yellow, red and blue beryls are possible but much more rare. Synthetic emerald became possible with the development of the flux growth process and is produced in this way and well as hydrothermal growth. Types of synthetic quartz include citrine, rose quartz, and amethyst. Natural occurring quartz is not rare, but is nevertheless synthetically produced as it has practical application outside of aesthetic purposes. Quartz generates an electric current when under pressure and
3219-486: Is equal to one millilitre. In industry, other larger or smaller units of mass and or volume are often more practical and US customary units may be used. See below for a list of some of the most common units of density. The litre and tonne are not part of the SI, but are acceptable for use with it, leading to the following units: Densities using the following metric units all have exactly the same numerical value, one thousandth of
3330-563: Is essential. Additionally, investing in community development projects, such as education and healthcare initiatives, can help alleviate poverty and empower marginalized communities dependent on the gemstone industry. Collaboration across sectors is crucial for fostering a more equitable and sustainable gemstone trade that benefits both producers and consumers while respecting human rights and environmental integrity. Synthetic gemstones are distinct from imitation or simulated gems. Synthetic gems are physically, optically, and chemically identical to
3441-419: Is heated, those stones should not be coated with boric acid (which can etch the surface) or any other substance. They do not have to be protected from burning, like a diamond (although the stones do need to be protected from heat stress fracture by immersing the part of the jewelry with stones in the water when metal parts are heated). The irradiation process is widely practiced in jewelry industry and enabled
Mineralogy - Misplaced Pages Continue
3552-403: Is necessary to have an understanding of the type of density being measured as well as the type of material in question. The density at all points of a homogeneous object equals its total mass divided by its total volume. The mass is normally measured with a scale or balance ; the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. To determine
3663-410: Is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones . The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. The faceting machine is used to hold the stone onto a flat lap for cutting and polishing
3774-450: 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
3885-453: Is small. The compressibility for a typical liquid or solid is 10 bar (1 bar = 0.1 MPa) and a typical thermal expansivity is 10 K . This roughly translates into needing around ten thousand times atmospheric pressure to reduce the volume of a substance by one percent. (Although the pressures needed may be around a thousand times smaller for sandy soil and some clays.) A one percent expansion of volume typically requires
3996-488: Is so great a difference in density between salt and fresh water that vessels laden with cargoes of the same weight almost sink in rivers, but ride quite easily at sea and are quite seaworthy. And an ignorance of this has sometimes cost people dear who load their ships in rivers. The following is a proof that the density of a fluid is greater when a substance is mixed with it. If you make water very salt by mixing salt in with it, eggs will float on it. ... If there were any truth in
4107-428: Is so much denser than air that the buoyancy effect is commonly neglected (less than one part in one thousand). Mass change upon displacing one void material with another while maintaining constant volume can be used to estimate the void fraction, if the difference in density of the two voids materials is reliably known. In general, density can be changed by changing either the pressure or the temperature . Increasing
4218-609: Is the absolute temperature . This means that the density of an ideal gas can be doubled by doubling the pressure, or by halving the absolute temperature. In the case of volumic thermal expansion at constant pressure and small intervals of temperature the temperature dependence of density is ρ = ρ T 0 1 + α ⋅ Δ T , {\displaystyle \rho ={\frac {\rho _{T_{0}}}{1+\alpha \cdot \Delta T}},} where ρ T 0 {\displaystyle \rho _{T_{0}}}
4329-473: 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 the lattice: reflection , rotation , inversion , and rotary inversion ,
4440-418: Is the densest known element at standard conditions for temperature and pressure . To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity " relative density " or " specific gravity ", i.e. the ratio of the density of the material to that of a standard material, usually water. Thus a relative density less than one relative to water means that
4551-487: Is the density at a reference temperature, α {\displaystyle \alpha } is the thermal expansion coefficient of the material at temperatures close to T 0 {\displaystyle T_{0}} . The density of a solution is the sum of mass (massic) concentrations of the components of that solution. Mass (massic) concentration of each given component ρ i {\displaystyle \rho _{i}} in
Mineralogy - Misplaced Pages Continue
4662-591: Is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume , although this is scientifically inaccurate – this quantity is more specifically called specific weight . For a pure substance the density has the same numerical value as its mass concentration . Different materials usually have different densities, and density may be relevant to buoyancy , purity and packaging . Osmium
4773-573: 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
4884-432: 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
4995-525: Is used in watches, clocks, and oscillators. Density Density ( volumetric mass density or specific mass ) is a substance's mass per unit of volume . The symbol most often used for density is ρ (the lower case Greek letter rho ), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume: ρ = m V , {\displaystyle \rho ={\frac {m}{V}},} where ρ
5106-479: 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
5217-446: The ancient Greeks , begins with a distinction between precious and semi-precious ; similar distinctions are made in other cultures. In modern use, the precious stones are emerald , ruby , sapphire and diamond , with all other gemstones being semi-precious. This distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent , with fine color in their purest forms (except for
5328-456: 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
5439-537: The displacement of the water. Upon this discovery, he leapt from his bath and ran naked through the streets shouting, "Eureka! Eureka!" ( Ancient Greek : Εύρηκα! , lit. 'I have found it'). As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment. The story first appeared in written form in Vitruvius ' books of architecture , two centuries after it supposedly took place. Some scholars have doubted
5550-472: 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
5661-415: The 19th century, amethyst was considered a "precious stone" as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine , peridot and cat's eye ( cymophane ) have been popular and hence been regarded as precious, thus reinforcing the notion that a mineral's rarity may have been implicated in its classification as a precious stone and thus contribute to its value. Today
SECTION 50
#17328486043795772-553: 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
5883-452: 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
5994-431: The accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time. Nevertheless, in 1586, Galileo Galilei , in one of his first experiments, made a possible reconstruction of how the experiment could have been performed with ancient Greek resources From the equation for density ( ρ = m / V ), mass density has any unit that
6105-518: The basis of their alleged healing powers. A gemstone that has been rising in popularity is Cuprian Elbaite Tourmaline which is also called "Paraiba Tourmaline". It was first discovered in the late 1980s in Paraíba, Brazil and later in Mozambique and Nigeria. It is famous for its glowing neon blue color. Paraiba Tourmaline has become one of the most popular gemstones in recent times thanks to its color and
6216-404: The body then can be expressed as m = ∫ V ρ ( r → ) d V . {\displaystyle m=\int _{V}\rho ({\vec {r}})\,dV.} In practice, bulk materials such as sugar, sand, or snow contain voids. Many materials exist in nature as flakes, pellets, or granules. Voids are regions which contain something other than
6327-407: The bottom of a fluid results in convection of the heat from the bottom to the top, due to the decrease in the density of the heated fluid, which causes it to rise relative to denser unheated material. The reciprocal of the density of a substance is occasionally called its specific volume , a term sometimes used in thermodynamics . Density is an intensive property in that increasing the amount of
6438-416: The case of non-compact materials, one must also take care in determining the mass of the material sample. If the material is under pressure (commonly ambient air pressure at the earth's surface) the determination of mass from a measured sample weight might need to account for buoyancy effects due to the density of the void constituent, depending on how the measurement was conducted. In the case of dry sand, sand
6549-450: 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
6660-455: The color from white to blue. Most green quartz (Oro Verde) are also irradiated to achieve the yellow-green color. Diamonds are mainly irradiated to become blue-green or green, although other colors are possible. When light-to-medium-yellow diamonds are treated with gamma rays they may become green; with a high-energy electron beam, blue. Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil
6771-475: The colorless diamond), and very hard with a hardness score of 8 to 10 on the Mohs scale . Other stones are classified by their color, translucency , and hardness. The traditional distinction does not necessarily reflect modern values; for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald. Another traditional term for semi-precious gemstones used in art history and archaeology
SECTION 60
#17328486043796882-717: 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
6993-405: The considered material. Commonly the void is air, but it could also be vacuum, liquid, solid, or a different gas or gaseous mixture. The bulk volume of a material —inclusive of the void space fraction — is often obtained by a simple measurement (e.g. with a calibrated measuring cup) or geometrically from known dimensions. Mass divided by bulk volume determines bulk density . This is not
7104-673: The constant discovery of new source locations. Determining a "country of origin" is thus much more difficult than determining other aspects of a gem (such as cut, clarity, etc.). Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate. A few gemstones are used as gems in the crystal or other forms in which they are found. Most, however, are cut and polished for usage as jewelry. The two main classifications are as follows: Stones which are opaque or semi-opaque such as opal , turquoise , variscite , etc. are commonly cut as cabochons. These gems are designed to show
7215-444: The creation of gemstone colors that do not exist or are extremely rare in nature. However, particularly when done in a nuclear reactor , the processes can make gemstones radioactive. Health risks related to the residual radioactivity of the treated gemstones have led to government regulations in many countries. Virtually all blue topaz , both the lighter and the darker blue shades such as "London" blue, has been irradiated to change
7326-559: 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
7437-414: 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,
7548-710: The density can be calculated. One dalton per cubic ångström is equal to a density of 1.660 539 066 60 g/cm . A number of techniques as well as standards exist for the measurement of density of materials. Such techniques include the use of a hydrometer (a buoyancy method for liquids), Hydrostatic balance (a buoyancy method for liquids and solids), immersed body method (a buoyancy method for liquids), pycnometer (liquids and solids), air comparison pycnometer (solids), oscillating densitometer (liquids), as well as pour and tap (solids). However, each individual method or technique measures different types of density (e.g. bulk density, skeletal density, etc.), and therefore it
7659-427: The density of a liquid or a gas, a hydrometer , a dasymeter or a Coriolis flow meter may be used, respectively. Similarly, hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object. If the body is not homogeneous, then its density varies between different regions of the object. In that case the density around any given location is determined by calculating
7770-488: The density of a small volume around that location. In the limit of an infinitesimal volume the density of an inhomogeneous object at a point becomes: ρ ( r → ) = d m / d V {\displaystyle \rho ({\vec {r}})=dm/dV} , where d V {\displaystyle dV} is an elementary volume at position r → {\displaystyle {\vec {r}}} . The mass of
7881-514: The earliest methods of gemstone treatment date back to the Minoan Age, for example foiling, which is where metal foil is used to enhance a gemstone's colour. Other methods recorded 2000 years ago in the book Natural History by Pliny the Elder include oiling and dyeing/staining. Heat can either improve or spoil gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating
7992-410: The early 1950s. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision). A mnemonic device , the "four Cs" (color, cut, clarity, and carats), has been introduced to help describe the factors used to grade
8103-410: The eye (brilliance). In its rough crystalline form, a diamond will do none of these things; it requires proper fashioning and this is called "cut". In gemstones that have color, including colored diamonds, the purity, and beauty of that color is the primary determinant of quality. Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have
8214-445: The eye as the perceived color. A ruby appears red because it absorbs all other colors of white light while reflecting red. A material which is mostly the same can exhibit different colors. For example, ruby and sapphire have the same primary chemical composition (both are corundum ) but exhibit different colors because of impurities which absorb and reflect different wavelengths of light depending on their individual compositions. Even
8325-439: The fact that these impurities can be "manipulated", thus changing the color of the gem. Gemstones are often treated to enhance the color or clarity of the stone. In some cases, the treatment applied to the gemstone can also increase its durability. Even though natural gemstones can be transformed using the traditional method of cutting and polishing, other treatment options allow the stone's appearance to be enhanced. Depending on
8436-476: 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
8547-451: The field of gemology . The first characteristic a gemologist uses to identify a gemstone is its chemical composition . For example, diamonds are made of carbon ( C ) and rubies of aluminium oxide ( Al 2 O 3 ). Many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic . Another term used is habit , the form the gem is usually found in. For example, diamonds, which have
8658-417: The flat facets. Rarely, some cutters use special curved laps to cut and polish curved facets. The color of any material is due to the nature of light itself. Daylight, often called white light, is all of the colors of the spectrum combined. When light strikes a material, most of the light is absorbed while a smaller amount of a particular frequency or wavelength is reflected. The part that is reflected reaches
8769-668: The gemstone trade no longer makes such a distinction. Many gemstones are used in even the most expensive jewelry, depending on the brand-name of the designer, fashion trends, market supply, treatments, etc. Nevertheless, diamonds, rubies, sapphires, and emeralds still have a reputation that exceeds those of other gemstones. Rare or unusual gemstones, generally understood to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite , axinite , cassiterite , clinohumite , painite and red beryl . Gemstone pricing and value are governed by factors and characteristics in
8880-425: The gemstone's durability to be increased. The socio-economic dynamics of the gemstone industry are shaped by market forces and consumer preferences and typically go undiscussed. Changes in demand and prices can significantly affect the livelihoods of those involved in gemstone mining and trade, particularly in developing countries where the industry serves as a crucial source of income. A situation that arises as
8991-419: The gods and replacing it with another, cheaper alloy . Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass; but the king did not approve of this. Baffled, Archimedes is said to have taken an immersion bath and observed from the rise of the water upon entering that he could calculate the volume of the gold wreath through
9102-595: 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
9213-686: 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
9324-521: 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
9435-422: 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,
9546-419: The look and color of the real stone but possess neither their chemical nor physical characteristics. In general, all are less hard than diamond. Moissanite actually has a higher refractive index than diamond, and when presented beside an equivalently sized and cut diamond will show more "fire". Cultured, synthetic, or "lab-created" gemstones are not imitations: The bulk mineral and trace coloring elements are
9657-435: The mineral species beryl . Gems are characterized in terms of their color (hue, tone and saturation), optical phenomena, luster, refractive index , birefringence , dispersion , specific gravity , hardness , cleavage , and fracture . They may exhibit pleochroism or double refraction . They may have luminescence and a distinctive absorption spectrum . Gemstones may also be classified in terms of their "water". This
9768-516: The most common on the market currently. Synthetic corundum includes ruby (red variation) and sapphire (other color variations), both of which are considered highly desired and valued. Ruby was the first gemstone to be synthesized by Auguste Verneuil with his development of the flame-fusion process in 1902. Synthetic corundum continues to be made typically by flame-fusion as it is most cost-effective, but can also be produced through flux growth and hydrothermal growth. The most common synthesized beryl
9879-538: The natural stone, but are created in a laboratory. Imitation or simulated stones are chemically different from the natural stone, but may appear quite similar to it; they can be more easily manufactured synthetic gemstones of a different mineral ( spinel ), glass, plastic, resins, or other compounds. Examples of simulated or imitation stones include cubic zirconia , composed of zirconium oxide, synthetic moissanite , and uncolored, synthetic corundum or spinels ; all of which are diamond simulants . The simulants imitate
9990-583: 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
10101-436: 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
10212-689: The pre-existing socio-economic disparities and obstructs community development such that the benefits of gemstone extraction may not adequately reach those directly involved in the process. Another such issue revolves around environmental degradation resulting from mining activities. Environmental degradation can pose long-term threats to ecosystems and biodiversity, further worsening the socio-economic state in affected regions. Unregulated mining practices often result in deforestation , soil erosion , and water contamination thus threatening ecosystems and biodiversity . Unregulated mining activity can also cause depletion of natural resources, thus diminishing
10323-416: The pressure always increases the density of a material. Increasing the temperature generally decreases the density, but there are notable exceptions to this generalization. For example, the density of water increases between its melting point at 0 °C and 4 °C; similar behavior is observed in silicon at low temperatures. The effect of pressure and temperature on the densities of liquids and solids
10434-804: The prevalence of illicit practices undermine market integrity and trust. The lack of transparency and accountability in the supply chain aggravates pre-existing inequalities, as middlemen and corporations often capture a disproportionate share of the profits. As a result, the unequal distribution of profits along the supply chain does little to improve socio-economic inequalities, particularly in regions where gemstones are mined. Addressing these socio-economic challenges requires intensive effort from various stakeholders, including governments, industry executives, and society, to promote sustainable practices and ensure equitable outcomes for all involved parties. Implementing and enforcing regulations to ensure fair labor practices, environmental sustainability, and ethical sourcing
10545-1012: The private Mim Mineral Museum in Beirut , Lebanon , have popular collections of mineral specimens on permanent display. Gemstone A gemstone (also called a fine gem , jewel , precious stone , semiprecious stone , or simply gem ) is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments . Certain rocks (such as lapis lazuli , opal , and obsidian ) and occasionally organic materials that are not minerals (such as amber , jet , and pearl ) may also be used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some softer minerals such as brazilianite may be used in jewelry because of their color or luster or other physical properties that have aesthetic value . However, generally speaking, soft minerals are not typically used as gemstones by virtue of their brittleness and lack of durability. Found all over
10656-450: The prospects for sustainable development . The environmental impact of gemstone mining not only poses a threat to ecosystems but also undermines the long-term viability of the industry by diminishing the quality and quantity of available resources. Furthermore, the gemstone industry is also susceptible to issues related to transparency and ethics, which impact both producers and consumers. The lack of standardized certification processes and
10767-507: The quality of the stone. These characteristics include clarity, rarity, freedom from defects, the beauty of the stone, as well as the demand for such stones. There are different pricing influencers for both colored gemstones, and for diamonds. The pricing on colored stones is determined by market supply-and-demand, but diamonds are more intricate. In the addition to the aesthetic and adorning/ornamental purpose of gemstones, there are many proponents of energy medicine who also value gemstones on
10878-698: 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
10989-531: The same in both. For example, diamonds , rubies , sapphires , and emeralds have been manufactured in labs that possess chemical and physical characteristics identical to the naturally occurring variety. Synthetic (lab created) corundum , including ruby and sapphire, is very common and costs much less than the natural stones. Small synthetic diamonds have been manufactured in large quantities as industrial abrasives , although larger gem-quality synthetic diamonds are becoming available in multiple carats. Whether
11100-426: The same named gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called " padparadscha sapphire ". This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition and structure, they are not exactly
11211-402: The same thing as the material volumetric mass density. To determine the material volumetric mass density, one must first discount the volume of the void fraction. Sometimes this can be determined by geometrical reasoning. For the close-packing of equal spheres the non-void fraction can be at most about 74%. It can also be determined empirically. Some bulk materials, however, such as sand, have
11322-492: The same. Every now and then an atom is replaced by a completely different atom, sometimes as few as one in a million atoms. These so-called impurities are sufficient to absorb certain colors and leave the other colors unaffected. For example, beryl , which is colorless in its pure mineral form, becomes emerald with chromium impurities. If manganese is added instead of chromium , beryl becomes pink morganite . With iron, it becomes aquamarine. Some gemstone treatments make use of
11433-404: The stone's color, luster and other surface properties as opposed to internal reflection properties like brilliance. Grinding wheels and polishing agents are used to grind, shape, and polish the smooth dome shape of the stones. Gems that are transparent are normally faceted, a method that shows the optical properties of the stone's interior to its best advantage by maximizing reflected light which
11544-460: The stories they tell about the lake in Palestine it would further bear out what I say. For they say if you bind a man or beast and throw him into it he floats and does not sink beneath the surface. In a well-known but probably apocryphal tale, Archimedes was given the task of determining whether King Hiero 's goldsmith was embezzling gold during the manufacture of a golden wreath dedicated to
11655-426: The substance floats in water. The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume. In most materials, heating
11766-524: The synthetic stone. Synthetics are made free of common naturally occurring impurities that reduce gem clarity or color unless intentionally added in order to provide a more drab, natural appearance, or to deceive an assayer. On the other hand, synthetics often show flaws not seen in natural stones, such as minute particles of corroded metal from lab trays used during synthesis. Some gemstones are more difficult to synthesize than others and not all stones are commercially viable to attempt to synthesize. These are
11877-419: The type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone. Before the innovation of modern-day tools, thousands of years ago, people were recorded to use a variety of techniques to treat and enhance gemstones. Some of
11988-546: The value in (kg/m ). Liquid water has a density of about 1 kg/dm , making any of these SI units numerically convenient to use as most solids and liquids have densities between 0.1 and 20 kg/dm . In US customary units density can be stated in: Imperial units differing from the above (as the Imperial gallon and bushel differ from the US units) in practice are rarely used, though found in older documents. The Imperial gallon
12099-423: 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 ,
12210-457: The world, the industry of coloured gemstones (i.e. anything other than diamonds) is currently estimated at US$ 1.55 billion as of 2023 and is projected to steadily increase to a value of US$ 4.46 billion by 2033. A gem expert is a gemologist , a gem maker is called a lapidarist or gemcutter ; a diamond cutter is called a diamantaire . The traditional classification in the West, which goes back to
12321-443: Was based on the concept that an Imperial fluid ounce of water would have a mass of one Avoirdupois ounce, and indeed 1 g/cm ≈ 1.00224129 ounces per Imperial fluid ounce = 10.0224129 pounds per Imperial gallon. The density of precious metals could conceivably be based on Troy ounces and pounds, a possible cause of confusion. Knowing the volume of the unit cell of a crystalline material and its formula weight (in daltons ),
#378621