Selenite known as satin spar, desert rose, or gypsum flower are four crystal structure varieties of the mineral gypsum. These four varieties of gypsum may be called selenite. All varieties of gypsum, including selenite and alabaster, are composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. Selenite contains no significant selenium, the similarity of the names of the substances coming from the Ancient Greek word for the Moon; some of the largest crystals found are of selenite, the largest specimen found in the Naica Mine's Cave of the Crystals being 12 metres long and weighing 55 tons. The etymology of selenite is through Middle English selenite, from Latin selenites, from Greek selēnitēs moonstone or stone of the moon, from selēnē; the ancients had a belief that certain transparent crystals waned with the moon. From the 15th century, "selenite" has referred to the variety of gypsum that occurs in transparent crystals or crystalline masses. All varieties of gypsum are soft minerals.
This is the most important identifying characteristic of gypsum, as any variety of gypsum can be scratched with a fingernail. Because gypsum has natural thermal insulating properties, all varieties feel warm to the touch. Though sometimes grouped together as "selenite", the four crystalline varieties have differences. General identifying descriptions of the related crystalline varieties are: most transparent and colorless: it is named after Greek σεληνη "the moon". If selenite crystals show translucency, and/or color, it is caused by the presence of other minerals, sometimes in druse druse is the crust of tiny, minute, or micro crystals that form or fuse either within or upon the surface of a rock vug, geode, or another crystal most silky and translucent. Rosette shaped gypsum with outer druse of sand or with sand throughout – most sand colored the desert rose name can be applied to barite desert roses – barite is a harder mineral with higher density rosette shaped gypsum with spreading fibers – can include outer druse the difference between desert roses and gypsum flowers is that desert roses look like roses, whereas gypsum flowers form a myriad of shapes Varieties of gypsum known as "satin spar" and "alabaster" are used for a variety of ornamental purposes like sculptures and a substitute for window glass.
But because of the long history of the commercial value and use of both gypsum and alabaster, the four crystalline varieties have been somewhat ignored, except as a curiosity or as rock collectibles. Crystal habit refers to the shapes. Selenite crystals occur as tabular and columnar crystals with no imperfections or inclusions, thereby can appear water or glass-like. Many collectible selenite crystals have interesting inclusions such as, accompanying related minerals, interior druse and fossils. In some rare instances, water was encased as a fluid inclusion. Selenite crystals sometimes form in thin tabular or mica-like sheets and have been used as glass panes as at Santa Sabina in Rome. Selenite crystals sometimes will exhibit bladed rosette habit with accompanying transparent, columnar crystals. Selenite crystals can be found both attached to a matrix or base rock, but can be found as entire free-floating crystals in clay beds. Satin spar is always prismatic and fibrous in a parallel crystal habit.
Satin spar occurs in seams, some of them quite long, is attached to a matrix or base rock. Desert roses are most bladed, exhibiting the familiar shape of a rose, always have an exterior druse. Desert roses are always unattached to a matrix or base rock. Gypsum flowers are most acicular, scaly and lenticular. Gypsum flowers most exhibit simple twinning. Selenite crystals can exhibit “arrow/spear-head” as well as “duck-bill” twins. Both selenite crystals and gypsum flowers sometimes form quite densely in acicular nets. Gypsum flowers are attached to a matrix or base rock. Gypsum crystals are colorless, gray, beige, pink, light red, green. Colors are caused by the presence of other mineral inclusions such as, copper ores and sulfides, iron ores, calcite and opal. Gypsum crystals can be transparent and opaque. Opacity can be caused by impurities, inclusions and crust, can occur in all four crystalline varieties. Both selenite and satin spar are glassy or vitreous and silky – on cleavage surfaces. Luster is not exhibited in the rosettes, due to their exterior druse.
Gypsum flowers exhibit more luster than desert r
Cerussite is a mineral consisting of lead carbonate, an important ore of lead. The name is from white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, in 1832 F. S. Beudant applied the name cruise to the mineral, whilst the present form, cerussite, is due to W. Haidinger. Miners' names in early use were white-lead-ore. Cerussite is isomorphous with aragonite. Like aragonite it is frequently twinned, the compound crystals being pseudo-hexagonal in form. Three crystals are twinned together on two faces of the prism, producing six-rayed stellate groups with the individual crystals intercrossing at angles of nearly 60°. Crystals are of frequent occurrence and they have bright and smooth faces; the mineral occurs in compact granular masses, sometimes in fibrous forms. The mineral is colorless or white, sometimes grey or greenish in tint and varies from transparent to translucent with an adamantine lustre, it is brittle, has a conchoidal fracture. It has a Mohs hardness of 3 to 3.75 and a specific gravity of 6.5.
A variety containing 7% of zinc carbonate, replacing lead carbonate, is known as iglesiasite, from Iglesias in Sardinia, where it is found. The mineral may be recognized by its characteristic twinning, in conjunction with the adamantine lustre and high specific gravity, it dissolves with effervescence in dilute nitric acid. A blowpipe test will cause it to fuse readily, gives indications for lead. Finely crystallized specimens have been obtained from the Friedrichssegen mine in Lahnstein in Rhineland-Palatinate, Johanngeorgenstadt in Saxony, Stříbro in the Czech Republic, Phoenixville in Pennsylvania, Broken Hill in New South Wales, several other localities. Delicate acicular crystals of considerable length were found long ago in the Pentire Glaze mine near St Minver in Cornwall. Cerussite is found in considerable quantities, has a lead content of up to 77.5%. Lead carbonate is insoluble in neutral water, but will dissolve in dilute acids. "White lead" is the key ingredient in lead paints. Ingestion of lead-based paint chips is the most common cause of lead poisoning in children.
Both "white lead" and lead acetate have been used in cosmetics throughout history, though this practice has ceased in Western countries. Venetian Ceruse – Cerussite-based cosmetic popularly thought to be worn by Elizabeth I of England Mineral galleries This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed.. "Cerussite". Encyclopædia Britannica. 5. Cambridge University Press. P. 762
Jadeite is a pyroxene mineral with composition NaAlSi2O6. It is monoclinic, it has a Mohs hardness of about 6.5 to 7.0 depending on the composition. The mineral is dense, with a specific gravity of about 3.4. The name jadeite is derived from the Spanish phrase "piedra de ijada" which means "stone of the side"; the Latin version of the name, lapis nephriticus, is the origin of the term nephrite, a variety of jade. Jadeite forms solid solutions with other pyroxene endmembers such as augite and diopside and kosmochlor. Pyroxenes rich in both the jadeite and augite endmembers are known as omphacite. Jadeite is formed in metamorphic rocks under high pressure and low temperature conditions. Albite is a common mineral of the Earth's crust, it has a specific gravity of about 2.6, much less than that of jadeite. With increasing pressure, albite breaks down to form the high-pressure assemblage of jadeite plus quartz. Minerals associated with jadeite include: glaucophane, muscovite, aragonite and quartz. Rocks that consist entirely of jadeite are called jadeitite.
In all well-documented occurrences, jadeitite appears to have formed from subduction zone fluids in association with serpentinite. Jadeitite is resistant to weathering, boulders of jadeitite released from the serpentine-rich environments in which they formed are found in a variety of environments. Jadeite's color ranges from white through pale apple green to deep jade green but can be blue-green, lavender and a multitude of other rare colors. Chloromelanite is a dark green to black variety. Color is affected by the presence of trace elements such as chromium and iron, its translucence varies from opaque to clear. Variations in color and translucence are found within a single specimen. Jadeite is reported from California, US. Over 180 axe heads made from jadeitite quarried in northern Italy in the Neolithic era have been found across the British Isles; because of the difficulty of working this material, all the axe heads of this type found are thought to have been non-utilitarian and to have represented some form of currency or be the products of gift exchange.
A great many jadeite beads and axe heads as well as the remains of jadeite workshops from the Neolithic era have been uncovered in Itoigawa, Japan. These beads and axes were traded throughout Japan and the Korean Peninsula and were produced by the world's oldest known jadeite-using culture, centered on the Itoigawa region. Jadeite is one of two minerals recognized as the gemstone jade; the other is nephrite. Jadeite from the Motagua Valley, was used by the Olmec and Maya peoples, as well as the indigenous peoples of Costa Rica. In the West, the most valued colors of jadeite are the intensely green, translucent varieties, though traditionally white has been considered the most valuable of the jades by the Chinese. Other colors, like "Olmec blue" jade, characterized by its deep blue-green, translucent hue with white flecking, are becoming more valued because of its unique beauty and historical use by the Mesoamerican Olmec and in Costa Rica, it is thus difficult to obtain and as yet too rare and little known to have attained great value as a gemstone.
The commercial quality of jade is determined by the degree of translucence, cleanness of color and purity of color. Other minerals such as serpentine or quartz are sold as jade, but the difference can be determined by cleavage and hardness. Clinopyroxene thermobarometry Costa Rican jade tradition Jade use in Mesoamerica
A crystal or crystalline solid is a solid material whose constituents are arranged in a ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations; the scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification; the word crystal derives from the Ancient Greek word κρύσταλλος, meaning both "ice" and "rock crystal", from κρύος, "icy cold, frost". Examples of large crystals include snowflakes and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever.
Examples of amorphous solids include glass and many plastics. Despite the name, lead crystal, crystal glass, related products are not crystals, but rather types of glass, i.e. amorphous solids. Crystals are used in pseudoscientific practices such as crystal therapy, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements; the scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. A crystal is a solid where the atoms form a periodic arrangement.. Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries.
Most macroscopic inorganic solids are polycrystalline, including all metals, ice, etc. Solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids called glassy, vitreous, or noncrystalline; these have no periodic order microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure is characterized by its unit cell, a small imaginary box containing one or more atoms in a specific spatial arrangement; the unit cells are stacked in three-dimensional space to form the crystal. The symmetry of a crystal is constrained by the requirement that the unit cells stack with no gaps. There are 219 possible crystal symmetries, called crystallographic space groups; these are grouped into 7 crystal systems, such as hexagonal crystal system. Crystals are recognized by their shape, consisting of flat faces with sharp angles.
These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is present and easy to see. Euhedral crystals are those with well-formed flat faces. Anhedral crystals do not because the crystal is one grain in a polycrystalline solid; the flat faces of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: they are planes of low Miller index. This occurs; as a crystal grows, new atoms attach to the rougher and less stable parts of the surface, but less to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, using them to infer the underlying crystal symmetry.
A crystal's habit is its visible external shape. This is determined by the crystal structure, the specific crystal chemistry and bonding, the conditions under which the crystal formed. By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock. Crystals found in rocks range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are found; as of 1999, the world's largest known occurring crystal is a crystal of beryl from Malakialina, Madagascar, 18 m long and 3.5 m in diameter, weighing 380,000 kg. Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock; the vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends on the conditions under which they solidified. Such rocks as granite, which have cooled slowly and under great pressures, have crystallized.
Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet of silica linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in kaolinite are known as china clay; the name "kaolin" is derived from "Gaoling", a Chinese village near Jingdezhen in southeastern China's Jiangxi Province. The name entered English in 1727 from the French version of the word: kaolin, following François Xavier d'Entrecolles's reports on the making of Jingdezhen porcelain. Kaolinite has a low shrink -- a low cation-exchange capacity, it is a soft, earthy white, produced by the chemical weathering of aluminium silicate minerals like feldspar. In many parts of the world it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield yellow, or light orange colors. Alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, United States.
Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodle or as liquid slurry. The chemical formula for kaolinite as used in mineralogy is Al2Si2O54, however, in ceramics applications the formula is written in terms of oxides, thus the formula for kaolinite is Al2O3 · 2SiO2 · 2H2O. Kaolinite group clays undergo a series of phase transformations upon thermal treatment in air at atmospheric pressure. Below 100 °C, exposure to dry air will remove liquid water from the kaolin; the end-state for this transformation is referred to as "leather dry". Between 100 °C and about 550 °C, any remaining liquid water is expelled from kaolinite; the end state for this transformation is referred to as "bone dry". Throughout this temperature range, the expulsion of water is reversible: if the kaolin is exposed to liquid water, it will be reabsorbed and disintegrate into its fine particulate form. Subsequent transformations are not reversible, represent permanent chemical changes. Endothermic dehydration of kaolinite begins at 550–600 °C producing disordered metakaolin, but continuous hydroxyl loss is observed up to 900 °C.
Although there was much disagreement concerning the nature of the metakaolin phase, extensive research has led to a general consensus that metakaolin is not a simple mixture of amorphous silica and alumina, but rather a complex amorphous structure that retains some longer-range order due to stacking of its hexagonal layers. Al 2 Si 2 O 5 4 ⟶ Al 2 Si 2 O 7 + 2 H 2 O Further heating to 925–950 °C converts metakaolin to an aluminium-silicon spinel, sometimes referred to as a gamma-alumina type structure: 2 Al 2 Si 2 O 7 ⟶ Si 3 Al 4 O 12 + SiO 2 Upon calcination above 1050 °C, the spinel phase nucleates and transforms to platelet mullite and crystalline cristobalite: 3 Si 3 Al 4 O 12 ⟶ 2 + 5 SiO 2 Finally, at 1400 °C the "needle" form of mullite appears, offering substantial increases in structural strength and heat resistance; this is a structural but not chemical transformation. See stoneware for more information on this form. Kaolinite is one of the most common minerals. Mantles of kaolinitic saprolite are common in Northern Europe.
The ages of these mantles are Mesozoic to Early Cenozoic. Kaolinite clay occurs in abundance in soils that have formed from the chemical weathering of rocks in hot, moist climates—for example in tropical rainforest areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolinite decreases, while the proportion of other clay minerals such as illite or smectite increases; such climatically-related differences in clay mineral content are used to infer changes in climates in the geological past, where ancient soils have been buried and preserved. In the Institut National pour l'Etude Agronomique au Congo Belge classification system, soils in which the clay fraction is predominantly kaolinite are called kaolisol. In the US, the main kaolin deposits are found in central Georgia, on a stretch of the Atlantic Seaboard fall line between Augusta and Macon; this area of thirteen counties is called the "white gold" belt. I
Galena called lead glance, is the natural mineral form of lead sulfide. It is an important source of silver. Galena is one of the most abundant and distributed sulfide minerals, it crystallizes in the cubic crystal system showing octahedral forms. It is associated with the minerals sphalerite and fluorite. Galena is the main ore of lead, used since ancient times; because of its somewhat low melting point, it was easy to liberate by smelting. It forms in low-temperature sedimentary deposits. In some deposits the galena contains about 1–2% silver, a byproduct that far outweighs the main lead ore in revenue. In these deposits significant amounts of silver occur as included silver sulfide mineral phases or as limited silver in solid solution within the galena structure; these argentiferous galenas have long been an important ore of silver. Galena deposits are found worldwide in various environments. Noted deposits include those at Freiberg in Saxony. In the United States, it occurs most notably in the Mississippi Valley type deposits of the Lead Belt in southeastern Missouri, in the Driftless Area of Illinois and Wisconsin.
Galena was a major mineral of the zinc-lead mines of the tri-state district around Joplin in southwestern Missouri and the adjoining areas of Kansas and Oklahoma. Galena is an important ore mineral in the silver mining regions of Colorado, Idaho and Montana. Of the latter, the Coeur d'Alene district of northern Idaho was most prominent. Galena is the official state mineral of the U. S. states of Wisconsin. The largest documented crystal of galena is composite cubo-octahedra from the Great Laxey Mine, Isle of Man, measuring 25 cm × 25 cm × 25 cm. Galena belongs to the octahedral sulfide group of minerals that have metal ions in octahedral positions, such as the iron sulfide pyrrhotite and the nickel arsenide niccolite; the galena group is named after its most common member, with other isometric members that include manganese bearing alabandite and niningerite. Divalent lead cations and sulfur anions form a close-packed cubic unit cell much like the mineral halite of the halide mineral group. Zinc, iron, antimony, arsenic and selenium occur in variable amounts in galena.
Selenium substitutes for sulfur in the structure constituting a solid solution series. The lead telluride mineral altaite has the same crystal structure as galena. Within the weathering or oxidation zone galena alters to cerussite. Galena exposed to acid mine drainage can be oxidized to anglesite by occurring bacteria and archaea, in a process similar to bioleaching. One of the oldest uses of galena was in the eye cosmetic kohl. In Ancient Egypt, this was applied around the eyes to reduce the glare of the desert sun and to repel flies, which were a potential source of disease. Galena is the primary ore of lead, used in making lead–acid batteries. Galena is mined for its silver content, such as at the Galena Mine in northern Idaho. Known as "potter's ore", galena is used in a green glaze applied to pottery. Galena is a semiconductor with a small band gap of about 0.4 eV, which found use in early wireless communication systems. It was used as the crystal in crystal radio receivers, in which it was used as a point-contact diode capable of rectifying alternating current to detect the radio signals.
The galena crystal was used with a sharp wire, known as a "cat's whisker" in contact with it. The operation of the radio required that the point of contact on the galena be shifted about to find a part of the crystal that acted as a rectifying diode. Making such wireless receivers was a popular home hobby in Britain and other European countries during the 1930s. Scientists associated with the investigation of the diode effect are Karl Ferdinand Braun and Jagadish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices. List of minerals Lead smelter Klein, Cornelis. Manual of Mineralogy. Wiley. Pp. 274–276. ISBN 0-471-80580-7. Case Studies in Environmental Medicine: Lead Toxicity. ToxFAQs: Lead. Mineral Information Institute entry for lead
Chewing gum is a soft, cohesive substance designed to be chewed without being swallowed. Modern chewing gum is composed of gum base, softeners/plasticizers, colors, a hard or powdered polyol coating, its texture is reminiscent of rubber because of the physical-chemical properties of its polymer and resin components, which contribute to its elastic-plastic, chewy characteristics. The cultural tradition of chewing gum seems to have developed through a convergent evolution process, as traces of this habit have arisen separately in many of the early civilizations; each of the early precursors to chewing gum were derived from natural growths local to the region and were chewed purely out the instinctual desire to masticate. Early chewers did not desire to derive nutritional benefits from their chewable substances, but at times sought taste stimuli and teeth cleaning or breath-freshening capabilities. Chewing gum in many forms has existed since the Neolithic period. 6,000-year-old chewing gum made from birch bark tar, with tooth imprints, has been found in Kierikki in Finland.
The tar from which the gums were made is believed to have antiseptic properties and other medicinal benefits. It is in this way different from most other early gum; the Mayans and Aztecs were the first to exploit the positive properties of gum, they used chicle, a natural tree gum, as a base for making a gum-like substance and to stick objects together in everyday use. Forms of chewing gums were chewed in Ancient Greece; the Ancient Greeks chewed mastic gum, made from the resin of the mastic tree. Mastic gum, like birch bark tar, has antiseptic properties and is believed to have been used to maintain oral health. Both chicle and mastic are tree resins. Many other cultures have chewed gum-like substances made from plants and resins. Although chewing gum can be traced back to civilizations around the world, the modernization and commercialization of this product took place in the United States; the American Indians chewed resin made from the sap of spruce trees. The New England settlers picked up this practice, in 1848, John B. Curtis developed and sold the first commercial chewing gum called The State of Maine Pure Spruce Gum.
In this way, the industrializing West, having forgotten about tree gums, rediscovered chewing gum through the First Americans. Around 1850 a gum made from paraffin wax, a petroleum product, was developed and soon exceeded the spruce gum in popularity. To sweeten these early gums, the chewer would make use of a plate of powdered sugar, which they would dip the gum into to maintain sweetness. William Semple filed an early patent on chewing gum, patent number 98,304, on December 28, 1869; the first flavored chewing gum was created in the 1860s by John Colgan, a Louisville, Kentucky pharmacist. Colgan mixed with powdered sugar the aromatic flavoring tolu, a powder obtained from an extract of the balsam tree, creating small sticks of flavored chewing gum he named "Taffy Tolu". Colgan lead the way in the manufacturing and packaging of chicle-based chewing gum, derived from Manilkara chicle, a tropical evergreen tree, he licensed a patent for automatically cutting chips of chewing gum from larger sticks: US 966,160 "Chewing Gum Chip Forming Machine" August 2, 1910 and a patent for automatically cutting wrappers for sticks of chewing gum: US 913,352 "Web-cutting attachment for wrapping-machines" February 23, 1909 from Louisville, Kentucky inventor James Henry Brady, an employee of the Colgan Gum Company.
Modern chewing gum was first developed in the 1860s when chicle was brought from Mexico by the former President, General Antonio Lopez de Santa Anna, to New York, where he gave it to Thomas Adams for use as a rubber substitute. Chicle did not succeed as a replacement for rubber, but as a gum, cut into strips and marketed as Adams New York Chewing Gum in 1871. Black Jack, flavored with licorice and Wrigley's Spearmint Gum were early popular gums that dominated the market and are all still around today. Chewing gum gained worldwide popularity through American GIs in WWII, who were supplied chewing gum as a ration and traded it with locals. Synthetic gums were first introduced to the U. S. after chicle no longer satisfied the needs of making good chewing gum. By the 1960s, US manufacturers had switched to butadiene-based synthetic rubber, as it was cheaper to manufacture. Gum base composition is considered proprietary information known by select individuals within each gum-manufacturing company.
Information about the other components of chewing gum are more accessible to the public and they are listed in Table 2. Table 2: Common Ingredients in the Formulation of Modern Chewing Gum Gum base is made of polymers and resins. Polymers, including elastomers, are responsible for the sticky nature of chewing gum. Plasticizers improve flexibility and reduce brittleness, contributing to the plastic and elastic nature of gum; the interactions of plasticizers within gum base are governed by solubility parameters, molecular weight, chemical structure. Resins compose the hydrophobic portion of the gum base, responsible for its chewiness. Although the exact ingredients and proportions used in each brand's gum base are trade secrets within the gum industry, Table 3 lists all of the natural and synthetic gum base components approved for use in the United States, demonstrating some examples of key gum base components. Table 3: Gum Base Ingredients Approved for Use by the U. S. Food and Drug Administration First, gum base is prepared through a melting and straining or filtering process.
The formulation for gum base is proprietary information known to fe