La Pita is an emerald mine located in the western belt of the Colombian emerald mining area. It is owned and operated by the Colombian company, Zuliana De Esmeraldas Ltda.
74-511: La Pita is one of Colombia's largest emerald mines in Colombia, tantamount to its competitor, previously called Puerto Arturo, at present known as the Muzo Mine . La Pita has been one of the biggest contributors to Colombia's emerald production at times producing more than 80% of the total output of emeralds in Colombia. La Pita was discovered when an access road was being built, the workers and owners of
148-401: A 30-year exploration/exploitation license, this title granted the exclusive right to extract the corresponding minerals and to conduct the necessary efforts to explore, exploit, process, transport and ship the relevant minerals. Site security currently has several weak points, from the working face to processing of potential ore. The mine is not currently managed with consideration for who is in
222-435: A Fe face-centered cubic sublattice into which the S 2 ions are embedded. (Note though that the iron atoms in the faces are not equivalent by translation alone to the iron atoms at the corners.) The pyrite structure is also seen in other MX 2 compounds of transition metals M and chalcogens X = O , S , Se and Te . Certain dipnictides with X standing for P , As and Sb etc. are also known to adopt
296-586: A foul odor and corrosion of copper wiring. In the United States, in Canada, and more recently in Ireland, where it was used as underfloor infill, pyrite contamination has caused major structural damage. Concrete exposed to sulfate ions, or sulfuric acid, degrades by sulfate attack : the formation of expansive mineral phases, such as ettringite (small needle crystals exerting a huge crystallization pressure inside
370-414: A hard, fissile, metamorphic rock known as slate . With continued increase in metamorphic grade the sequence is phyllite , then schist and finally gneiss . Shale is the most common source rock for hydrocarbons ( natural gas and petroleum ). The lack of coarse sediments in most shale beds reflects the absence of strong currents in the waters of the depositional basin. These might have oxygenated
444-530: A sample of pyrite was placed against a circular file to strike the sparks needed to fire the gun. Pyrite is used with flintstone and a form of tinder made of stringybark by the Kaurna people of South Australia , as a traditional method of starting fires. Pyrite has been used since classical times to manufacture copperas ( ferrous sulfate ). Iron pyrite was heaped up and allowed to weather (an example of an early form of heap leaching ). The acidic runoff from
518-584: A simple liquid-phase exfoliation route. This is the first study to demonstrate the production of non-layered 2D-platelets from 3D bulk FeS 2 . Furthermore, they have used these 2D-platelets with 20% single walled carbon-nanotube as an anode material in lithium-ion batteries, reaching a capacity of 1000 mAh/g close to the theoretical capacity of FeS 2 . In 2021, a natural pyrite stone has been crushed and pre-treated followed by liquid-phase exfoliation into two-dimensional nanosheets, which has shown capacities of 1200 mAh/g as an anode in lithium-ion batteries. From
592-458: Is cubic and was among the first crystal structures solved by X-ray diffraction . It belongs to the crystallographic space group Pa 3 and is denoted by the Strukturbericht notation C2. Under thermodynamic standard conditions the lattice constant a {\displaystyle a} of stoichiometric iron pyrite FeS 2 amounts to 541.87 pm . The unit cell is composed of
666-404: Is a carbonate altered, with minor content kaolinite altered clasts, localized fluorite matrix, polymicitic carbonate altered shale and carbonate vein clasts, laminated to massive euhedral to anhedral carbonate matrix, chaotic order, clast-supported to matrix-support, fine to very coarse unsorted sharp clast contacts, sub-angular to angular. At present the mine is focused only on the footwall of
740-404: Is a common accessory mineral in igneous rocks, where it also occasionally occurs as larger masses arising from an immiscible sulfide phase in the original magma. It is found in metamorphic rocks as a product of contact metamorphism . It also forms as a high-temperature hydrothermal mineral , though it occasionally forms at lower temperatures. Pyrite occurs both as a primary mineral, present in
814-417: Is a substantial amount of material being moved out of the mine and into public area, with only the identified mineralization isolated, but emeralds being present in the other material after. Although effort is made to capture emeralds coming off the face, it has been demonstrated that there are emeralds winding up in the tailings with regularity, of variable quality. The two primary security issues are, access to
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#1733085399942888-460: Is about 1 atm . A newer commercial use for pyrite is as the cathode material in Energizer brand non-rechargeable lithium metal batteries . Pyrite is a semiconductor material with a band gap of 0.95 eV . Pure pyrite is naturally n-type, in both crystal and thin-film forms, potentially due to sulfur vacancies in the pyrite crystal structure acting as n-dopants. During the early years of
962-458: Is accelerated by the action of Acidithiobacillus bacteria which oxidize pyrite to first produce ferrous ions ( Fe ), sulfate ions ( SO 4 ), and release protons ( H , or H 3 O ). In a second step, the ferrous ions ( Fe ) are oxidized by O 2 into ferric ions ( Fe ) which hydrolyze also releasing H ions and producing FeO(OH). These oxidation reactions occur more rapidly when pyrite
1036-1201: Is accompanied by telogenesis , the third and final stage of diagenesis. As erosion reduces the depth of burial, renewed exposure to meteoric water produces additional changes to the shale, such as dissolution of some of the cement to produce secondary porosity . Pyrite may be oxidized to produce gypsum . Black shales are dark, as a result of being especially rich in unoxidized carbon . Common in some Paleozoic and Mesozoic strata , black shales were deposited in anoxic , reducing environments, such as in stagnant water columns. Some black shales contain abundant heavy metals such as molybdenum , uranium , vanadium , and zinc . The enriched values are of controversial origin, having been alternatively attributed to input from hydrothermal fluids during or after sedimentation or to slow accumulation from sea water over long periods of sedimentation. Fossils , animal tracks or burrows and even raindrop impressions are sometimes preserved on shale bedding surfaces. Shales may also contain concretions consisting of pyrite, apatite , or various carbonate minerals. Shales that are subject to heat and pressure of metamorphism alter into
1110-423: Is accounted for by point symmetry groups C 3 i and C 3 , respectively. The missing center of inversion at S lattice sites has important consequences for the crystallographic and physical properties of iron pyrite. These consequences derive from the crystal electric field active at the sulfur lattice site, which causes a polarization of S ions in the pyrite lattice. The polarisation can be calculated on
1184-554: Is also the fastest growing in terms of the unroasted iron pyrites imports, with a CAGR of +27.8% from 2007 to 2016. In July 2020 scientists reported that they have observed a voltage-induced transformation of normally diamagnetic pyrite into a ferromagnetic material, which may lead to applications in devices such as solar cells or magnetic data storage. Researchers at Trinity College Dublin , Ireland have demonstrated that FeS 2 can be exfoliated into few-layers just like other two-dimensional layered materials such as graphene by
1258-522: Is brighter yellow with a greenish hue when wet and is softer (3.5–4 on Mohs' scale). Arsenopyrite (FeAsS) is silver white and does not become more yellow when wet. Iron pyrite is unstable when exposed to the oxidizing conditions prevailing at the Earth's surface: iron pyrite in contact with atmospheric oxygen and water, or damp, ultimately decomposes into iron oxyhydroxides ( ferrihydrite , FeO(OH)) and sulfuric acid ( H 2 SO 4 ). This process
1332-443: Is brittle, gold is malleable. Natural gold tends to be anhedral (irregularly shaped without well defined faces), whereas pyrite comes as either cubes or multifaceted crystals with well developed and sharp faces easy to recognise. Well crystallised pyrite crystals are euhedral ( i.e. , with nice faces). Pyrite can often be distinguished by the striations which, in many cases, can be seen on its surface. Chalcopyrite ( CuFeS 2 )
1406-420: Is characterized by its tendency to split into thin layers ( laminae ) less than one centimeter in thickness. This property is called fissility . Shale is the most common sedimentary rock. The term shale is sometimes applied more broadly, as essentially a synonym for mudrock , rather than in the narrower sense of clay-rich fissile mudrock. Shale typically exhibits varying degrees of fissility. Because of
1480-485: Is common to find pyrite and calcite veins. These claystones are interspersed with sandy siltstones and quartz sandstones. Towards the middle of the segment arise shales and albitized limestone, somewhat calcareous. At this level appear a brecciated and mineralized zone with veins of calcite and sheets of oxidized sulphides. The upper part of the segment is interspersed with layers of gray claystones with layers of siltstones containing fauna depicted in ammonite molds. At
1554-638: Is composed of about 58% clay minerals, 28% quartz, 6% feldspar , 5% carbonate minerals, and 2% iron oxides . Most of the quartz is detrital (part of the original sediments that formed the shale) rather than authigenic (crystallized within the shale after deposition). Shales and other mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale. Black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron (Fe ) and sulfur (S ). Amorphous iron sulfide , along with carbon, produce
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#17330853999421628-540: Is derived from the Greek πυρίτης λίθος ( pyritēs lithos ), 'stone or mineral which strikes fire', in turn from πῦρ ( pŷr ), 'fire'. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel ; Pliny the Elder described one of them as being brassy, almost certainly a reference to what is now called pyrite. By Georgius Agricola 's time, c. 1550 ,
1702-430: Is evidence that shale acts as a semipermeable medium, allowing water to pass through while retaining dissolved salts. The fine particles that compose shale can remain suspended in water long after the larger particles of sand have been deposited. As a result, shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas , on floodplains and offshore below
1776-449: Is finely dispersed (framboidal crystals initially formed by sulfate reducing bacteria (SRB) in argillaceous sediments or dust from mining operations). Pyrite oxidation by atmospheric O 2 in the presence of moisture ( H 2 O ) initially produces ferrous ions ( Fe ) and sulfuric acid which dissociates into sulfate ions and protons , leading to acid mine drainage (AMD). An example of acid rock drainage caused by pyrite
1850-564: Is immediately above the calcareous rocks, in the La Pita Mine has a thickness of approximately 30 metres (98 ft), and at the Totumos Mine can reach to 50 metres (160 ft). This unit in the area of Coscuez and Muzo presents emeralds; its characteristic remains limestone in layers of calcareous siltstones interspersed with calcareous claystones. To the south of the area, this unit presents similar characteristics. A stratigraphic column along
1924-582: Is mining emeralds from the Muzo Formation, operations are currently focused wholly in the footwall of the Río Minero Fault. The property lies on a productive portion of the fault, with ~1 km of the NNE, moderate to steeply dipping fault (~025/75(?)) running along the long-axis of the property. The Rio Minero fault is characterized by an ~80m wide, very irregular, but sharp contact breccia zone. This breccia
1998-455: Is more likely to form nonfissile mudstone than shale. On the other hand, black shales often have very pronounced fissility ( paper shales ) due to binding of hydrocarbon molecules to the faces of the clay particles, which weakens the binding between particles. Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as
2072-453: Is not a formally recognised mineral, and is named after the Peruvian scientist Jose J. Bravo (1874–1928). Pyrite is distinguishable from native gold by its hardness, brittleness and crystal form. Pyrite fractures are very uneven , sometimes conchoidal because it does not cleave along a preferential plane. Native gold nuggets , or glitters, do not break but deform in a ductile way. Pyrite
2146-452: Is reduced. In addition to this physical compaction, chemical compaction may take place via pressure solution . Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. It is during compaction that shale develops its fissility, likely through mechanical compaction of
2220-430: Is sprayed onto the exposed coal surfaces to reduce the hazard of dust explosions . This has the secondary benefit of neutralizing the acid released by pyrite oxidation and therefore slowing the oxidation cycle described above, thus reducing the likelihood of spontaneous combustion. In the long term, however, oxidation continues, and the hydrated sulfates formed may exert crystallization pressure that can expand cracks in
2294-419: Is the 2015 Gold King Mine waste water spill . Pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion . The solution is the use of buffer blasting and the use of various sealing or cladding agents to hermetically seal the mined-out areas to exclude oxygen. In modern coal mines, limestone dust
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2368-566: Is used to make marcasite jewelry . Marcasite jewelry, using small faceted pieces of pyrite, often set in silver , has been made since ancient times and was popular in the Victorian era . At the time when the term became common in jewelry making, "marcasite" referred to all iron sulfides including pyrite, and not to the orthorhombic FeS 2 mineral marcasite which is lighter in color, brittle and chemically unstable, and thus not suitable for jewelry making. Marcasite jewelry does not actually contain
2442-399: The U.S. Gulf Coast . As sediments continue to accumulate, the older, more deeply buried sediments begin to undergo diagenesis . This mostly consists of compaction and lithification of the clay and silt particles. Early stages of diagenesis, described as eogenesis , take place at shallow depths (a few tens of meters) and are characterized by bioturbation and mineralogical changes in
2516-402: The chemical formula Fe S 2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral . Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold , hence the well-known nickname of fool's gold . The color has also led to the nicknames brass , brazzle , and brazil , primarily used to refer to pyrite found in coal . The name pyrite
2590-651: The wave base . Thick deposits of shale are found near ancient continental margins and foreland basins . Some of the most widespread shale formations were deposited by epicontinental seas . Black shales are common in Cretaceous strata on the margins of the Atlantic Ocean , where they were deposited in fault -bounded silled basins associated with the opening of the Atlantic during the breakup of Pangaea . These basins were anoxic, in part because of restricted circulation in
2664-432: The 20th century, pyrite was used as a mineral detector in radio receivers, and is still used by crystal radio hobbyists. Until the vacuum tube matured, the crystal detector was the most sensitive and dependable detector available—with considerable variation between mineral types and even individual samples within a particular type of mineral. Pyrite detectors occupied a midway point between galena detectors and
2738-553: The La Palma-Yacopí road, shows that this unit is composed of a black marl with a solid appearance with black calcareous claystone intercalations. In the upper part, intercalations of black shale with gypsum flakes and abundant pyritic micritical concretions appear, some with ammonites. The La Pita concession agreement is active and registered with the National Mining Agency of Colombia. The title holders of Las Pita have
2812-650: The National Armed Forces of Colombia. This presence provides for a very secure work place and community support, where the police and military often participate in community social projects ranging from building homes, aqueducts and road maintenance. Shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin , Al 2 Si 2 O 5 ( OH ) 4 ) and tiny fragments ( silt -sized particles) of other minerals, especially quartz and calcite . Shale
2886-452: The arrangement of the metal and diatomic anions differ from that of pyrite. Despite its name, chalcopyrite ( CuFeS 2 ) does not contain dianion pairs, but single S sulfide anions. Pyrite usually forms cuboid crystals, sometimes forming in close association to form raspberry-shaped masses called framboids . However, under certain circumstances, it can form anastomosing filaments or T-shaped crystals. Pyrite can also form shapes almost
2960-426: The basis of higher-order Madelung constants and has to be included in the calculation of the lattice energy by using a generalised Born–Haber cycle . This reflects the fact that the covalent bond in the sulfur pair is inadequately accounted for by a strictly ionic treatment. Arsenopyrite has a related structure with heteroatomic As–S pairs rather than S-S pairs. Marcasite also possesses homoatomic anion pairs, but
3034-421: The black coloration. Because amorphous iron sulfide gradually converts to pyrite , which is not an important pigment, young shales may be quite dark from their iron sulfide content, in spite of a modest carbon content (less than 1%), while a black color in an ancient shale indicates a high carbon content. Most shales are marine in origin, and the groundwater in shale formations is often highly saline . There
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3108-503: The bottom of this unit is the La Marina Mine and to the south the emerald mines of La Pita, Consorcio, Totumos, Polveros and others. The first calcareous package becomes thicker towards the south, it has a thickness of 2 metres (6.6 ft), and in the sector of Totumos and Polveros reaches 45 metres (148 ft), and is composed of intercalations of limestone ( micrite ), loam and sandy siltstones . The zone of hydrothermal breccias that
3182-506: The clumps of clay particles produced by flocculation vary in size from a few tens of microns to over 700 microns in diameter. The floccules start out water-rich, but much of the water is expelled from the floccules as the clay minerals bind more tightly together over time (a process called syneresis ). Clay pelletization by organisms that filter feed is important where flocculation is inhibited. Filter feeders produce an estimated 12 metric tons of clay pellets per square kilometer per year along
3256-408: The color of the rock. Red, brown and green colors are indicative of ferric oxide ( hematite – reds), iron hydroxide ( goethite – browns and limonite – yellow), or micaceous minerals ( chlorite , biotite and illite – greens). The color shifts from reddish to greenish as iron in the oxidized ( ferric ) state is converted to iron in the reduced ( ferrous ) state. Black shale results from
3330-438: The concrete pores) and gypsum creates inner tensile forces in the concrete matrix which destroy the hardened cement paste, form cracks and fissures in concrete, and can lead to the ultimate ruin of the structure. Normalized tests for construction aggregate certify such materials as free of pyrite or marcasite. Pyrite is the most common of sulfide minerals and is widespread in igneous, metamorphic, and sedimentary rocks. It
3404-402: The context of underground coal mining , shale was frequently referred to as slate well into the 20th century. Black shale associated with coal seams is called black metal. [REDACTED] Media related to Shale at Wikimedia Commons Pyrite The mineral pyrite ( / ˈ p aɪ r aɪ t / PY -ryte ), or iron pyrite , also known as fool's gold , is an iron sulfide with
3478-467: The fault itself. Muzo Formation (K1m - Hauterivian-Barremian age), outcropping in the sector of Las Pavas, Peñas Blancas, Coscuez, also appears in Vélez , Chiquinquirá and La Palma. It is part of the flanks of La Chapa-Borbur Anticlinal, also observed in the syncline of Otanche , in the sector of Coscuez . In the region of Muzo and Calcetero, the formation is also part of the syncline of El Almendro and forms
3552-480: The fault, exploiting oblique fractures in the Muzo Formation shales of the western flank of the fault. There appears to be a periodicity to the occurrence of variable thickness (1 to 30 centimetres (0.39 to 11.81 in)) calcite veins (observed between 070/35 and 320/65 orientations), that are the primary target for emerald production. The intersections of vein sets are a fertile setting and may represent an upgrading feature. Where these secondary fractures intersect with
3626-419: The gold is "invisible gold" incorporated into the pyrite (see Carlin-type gold deposit ). It has been suggested that the presence of both gold and arsenic is a case of coupled substitution but as of 1997 the chemical state of the gold remained controversial. Pyrite gained a brief popularity in the 16th and 17th centuries as a source of ignition in early firearms , most notably the wheellock , where
3700-585: The heap was then boiled with iron to produce iron sulfate. In the 15th century, new methods of such leaching began to replace the burning of sulfur as a source of sulfuric acid . By the 19th century, it had become the dominant method. Pyrite remains in commercial use for the production of sulfur dioxide , for use in such applications as the paper industry , and in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS ( iron(II) sulfide ) and elemental sulfur starts at 540 °C (1,004 °F); at around 700 °C (1,292 °F), p S 2
3774-424: The land descended towards Río Minero and noticed a yellowish patch of earth accompanied by the black carbonate altered shales of the Muzo Formation. This area is known as Amariallal and marked the establishment of La Pita Mine. The entrance of the mine was first opened in a ravine at the bottom of the mountain near Río Minero and extends approximately 500 metres (1,600 ft) until the tunnel makes contact with
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#17330853999423848-474: The mine site when the workings are open and ore processing. Porto Gringo access to the north may represent the greatest weakness to securing the site right now, because of the agreement to allow access to the neighbouring operation. The mining region, despite its poor reputation is actually safe and community orientated, the violence is now a faint memory of the past. Security in the mine is a collaboration between private security, National Police of Colombia and
3922-400: The mine when it is open and material is not properly processed before being dumped and accessed by the general public. Improvement in security would be relatively simple both from a capital expenditure and implementation perspective. There are 4 points of access, which can be controlled by guards, cameras and doors/walls. The ore would need to be handled differently than it currently is, as there
3996-592: The mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. The clay minerals may be altered as well. For example, smectite is altered to illite at temperatures of about 55 to 200 °C (130 to 390 °F), releasing water in the process. Other alteration reactions include the alteration of smectite to chlorite and of kaolinite to illite at temperatures between 120 and 150 °C (250 and 300 °F). Because of these reactions, illite composes 80% of Precambrian shales, versus about 25% of young shales. Unroofing of buried shale
4070-420: The mineral marcasite. The specimens of pyrite, when it appears as good quality crystals, are used in decoration. They are also very popular in mineral collecting. Among the sites that provide the best specimens are Soria and La Rioja provinces (Spain). In value terms, China ($ 47 million) constitutes the largest market for imported unroasted iron pyrites worldwide, making up 65% of global imports. China
4144-450: The more mechanically complicated perikon mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A germanium diode detector. Pyrite has been proposed as an abundant, non-toxic, inexpensive material in low-cost photovoltaic solar panels. Synthetic iron sulfide was used with copper sulfide to create the photovoltaic material. More recent efforts are working toward thin-film solar cells made entirely of pyrite. Pyrite
4218-433: The narrow Atlantic, and in part because the very warm Cretaceous seas lacked the circulation of cold bottom water that oxygenates the deep oceans today. Most clay must be deposited as aggregates and floccules, since the settling rate of individual clay particles is extremely slow. Flocculation is very rapid once the clay encounters highly saline sea water. Whereas individual clay particles are less than 4 microns in size,
4292-595: The nucleus of the Pauna Anticlinal. This unit houses most of the emerald-producing mines in the region such as Coscuez. The Muzo Formation is a generally calcareous sequence, while to the north of the Ibacapí Fault it is observed to be weathered and its calcareous composition is not recognized. To the north of Pauna the formation has a siliceous character. In general it is composed of dark gray calcareous claystones with lenses and limestone concretions. Additionally, it
4366-415: The original open framework of clay particles. The particles become strongly oriented into parallel layers that give the shale its distinctive fabric. Fissility likely develops early in the compaction process, at relatively shallow depth, since fissility does not seem to vary with depth in thick formations. Kaolinite flakes have less tendency to align in parallel layers than other clays, so kaolinite-rich clay
4440-706: The original sediments, and as a secondary mineral, deposited during diagenesis . Pyrite and marcasite commonly occur as replacement pseudomorphs after fossils in black shale and other sedimentary rocks formed under reducing environmental conditions. Pyrite is common as an accessory mineral in shale, where it is formed by precipitation from anoxic seawater, and coal beds often contain significant pyrite. Notable deposits are found as lenticular masses in Virginia, U.S., and in smaller quantities in many other locations. Large deposits are mined at Rio Tinto in Spain and elsewhere in
4514-444: The oxidation state of molybdenum is Mo . The mineral arsenopyrite has the formula Fe As S. Whereas pyrite has [S 2 ] units, arsenopyrite has [AsS] units, formally derived from deprotonation of arsenothiol (H 2 AsSH). Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe [AsS] . Iron-pyrite FeS 2 represents the prototype compound of the crystallographic pyrite structure. The structure
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#17330853999424588-631: The parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable bedding planes . Non-fissile rocks of similar composition and particle size (less than 0.0625 mm) are described as mudstones (1/3 to 2/3 silt particles) or claystones (less than 1/3 silt). Rocks with similar particle sizes but with less clay (greater than 2/3 silt) and therefore grittier are siltstones . Shales are typically gray in color and are composed of clay minerals and quartz grains. The addition of variable amounts of minor constituents alters
4662-528: The perspective of classical inorganic chemistry , which assigns formal oxidation states to each atom, pyrite and marcasite are probably best described as Fe [S 2 ] . This formalism recognizes that the sulfur atoms in pyrite occur in pairs with clear S–S bonds. These persulfide [ S–S ] units can be viewed as derived from hydrogen disulfide , H 2 S 2 . Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast, molybdenite , Mo S 2 , features isolated sulfide S centers and
4736-817: The presence of greater than one percent carbonaceous material and indicates a reducing environment. Pale blue to blue-green shales typically are rich in carbonate minerals . Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite , montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites , whereas in older rocks (especially in mid-to early Paleozoic shales) illites predominate. The transformation of smectite to illite produces silica , sodium , calcium , magnesium , iron and water. These released elements form authigenic quartz , chert , calcite , dolomite , ankerite , hematite and albite , all trace to minor (except quartz) minerals found in shales and other mudrocks. A typical shale
4810-480: The primary vein orientation, anecdotally it has been observed that there appears to be an improvement in both quality (colour and clarity) as well as, sometimes, quantity/size. These oblique vein sets (which may simply be conjugate fractures as a product of how the faulting influenced the host Muzo Formation (rheology during formation)) represent the primary source of emeralds in the current operations at La Pita. These vein sets are productive up to several meters away from
4884-497: The principle fault line running through the length of the La Pita property. La Pita is north of neighboring mine Cunas. Previously, a dispute between the two mines existed and both groups founded a mining agreement, that is defunct today. The agreement proposed that mining 35 metres (115 ft) north and south of the border between the mining districts was allowed by both parties. Today, the building structures and campsite are located on
4958-510: The property of Cunas. Recently, La Pita had entered into an agreement with a publicly traded company, FURA Emeralds Inc. This has since been terminated. Following that, a Canadian company entered into a non-binding agreement and was unable to successfully close on the contract. In 2016, a third company was entering into agreements for full operation at La Pita Mine and to acquire a stake in Zuliana De Esmeraldas Ltda. La Pita mine
5032-685: The pyrite structure. The Fe atoms are bonded to six S atoms, giving a distorted octahedron. The material is a semiconductor . The Fe ions is usually considered to be low spin divalent state (as shown by Mössbauer spectroscopy as well as XPS). The material as a whole behaves as a Van Vleck paramagnet , despite its low-spin divalency. The sulfur centers occur in pairs, described as S 2 . Reduction of pyrite with potassium gives potassium dithioferrate , KFeS 2 . This material features ferric ions and isolated sulfide (S ) centers. The S atoms are tetrahedral, being bonded to three Fe centers and one other S atom. The site symmetry at Fe and S positions
5106-444: The richest source rocks may contain as much as 40% organic matter. The organic matter in shale is converted over time from the original proteins, polysaccharides , lipids , and other organic molecules to kerogen , which at the higher temperatures found at greater depths of burial is further converted to graphite and petroleum. Before the mid-19th century, the terms slate , shale and schist were not sharply distinguished. In
5180-636: The rock and lead eventually to roof fall . Building stone containing pyrite tends to stain brown as pyrite oxidizes. This problem appears to be significantly worse if any marcasite is present. The presence of pyrite in the aggregate used to make concrete can lead to severe deterioration as pyrite oxidizes. In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to pyrite oxidation, followed by microbial sulfate reduction which released hydrogen sulfide gas ( H 2 S ). These problems included
5254-560: The same as a regular dodecahedron , known as pyritohedra, and this suggests an explanation for the artificial geometrical models found in Europe as early as the 5th century BC. Cattierite ( Co S 2 ), vaesite ( Ni S 2 ) and hauerite ( Mn S 2 ), as well as sperrylite ( Pt As 2 ) are similar in their structure and belong also to the pyrite group. Bravoite is a nickel-cobalt bearing variety of pyrite, with > 50% substitution of Ni for Fe within pyrite. Bravoite
5328-433: The sediments, with only slight compaction. Pyrite may be formed in anoxic mud at this stage of diagenesis. Deeper burial is accompanied by mesogenesis , during which most of the compaction and lithification takes place. As the sediments come under increasing pressure from overlying sediments, sediment grains move into more compact arrangements, ductile grains (such as clay mineral grains) are deformed, and pore space
5402-487: The term had become a generic term for all of the sulfide minerals . Pyrite is usually found associated with other sulfides or oxides in quartz veins , sedimentary rock , and metamorphic rock , as well as in coal beds and as a replacement mineral in fossils , but has also been identified in the sclerites of scaly-foot gastropods . Despite being nicknamed "fool's gold", pyrite is sometimes found in association with small quantities of gold. A substantial proportion of
5476-414: The waters and destroyed organic matter before it could accumulate. The absence of carbonate rock in shale beds reflects the absence of organisms that might have secreted carbonate skeletons, also likely due to an anoxic environment. As a result, about 95% of organic matter in sedimentary rocks is found in shales and other mudrocks. Individual shale beds typically have an organic matter content of about 1%, but
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