Lustre (mineralogy)
Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux, meaning "light", implies radiance, gloss, or brilliance. A range of terms are used to describe lustre, such as earthy, metallic and silky; the term vitreous refers to a glassy lustre. A list of these terms is given below. Lustre varies over a wide continuum, so there are no rigid boundaries between the different types of lustre; the terms are combined to describe intermediate types of lustre. Some minerals exhibit unusual optical phenomena, such as asterism or chatoyancy. A list of such phenomena is given below. Adamantine minerals possess a superlative lustre, most notably seen in diamond; such minerals are transparent or translucent, have a high refractive index. Minerals with a true adamantine lustre are uncommon, with examples being cerussite and cubic zirconia. Minerals with a lesser degree of lustre are referred to as subadamantine, with some examples being garnet and corundum.
Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, approximating a Lambertian reflector. An example is kaolinite. A distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, having less lustre. Greasy minerals resemble grease. A greasy lustre occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite, jadeite. Many minerals with a greasy lustre feel greasy to the touch. Metallic minerals have the lustre of polished metal, with ideal surfaces will work as a reflective surface. Examples include galena and magnetite. Pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls; such minerals possess perfect cleavage, with examples including stilbite. Resinous minerals have the appearance of chewing gum or plastic. A principal example is amber, a form of fossilized resin.
Silky minerals have a parallel arrangement of fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos and the satin spar variety of gypsum. A fibrous lustre has a coarser texture. Submetallic minerals are duller and less reflective. A submetallic lustre occurs in near-opaque minerals with high refractive indices, such as sphalerite and cuprite. Vitreous minerals have the lustre of glass; this type of lustre is one of the most seen, occurs in transparent or translucent minerals with low refractive indices. Common examples include calcite, topaz, beryl and fluorite, among others. Waxy minerals have a lustre resembling wax. Examples include chalcedony. Asterism is the display of a star-shaped luminous area, it is seen in some rubies, where it is caused by impurities of rutile. It can occur in garnet and spinel. Aventurescence is a reflectance effect like that of glitter, it arises from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they influence the material's body colour.
In aventurine quartz, chrome-bearing fuchsite makes for a green stone and various iron oxides make for a red stone. Chatoyant minerals display luminous bands; such minerals are composed of parallel fibers, which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light. The most famous examples are tiger's eye and cymophane, but the effect may occur in other minerals such as aquamarine and tourmaline. Color change is most found in alexandrite, a variety of chrysoberyl gemstones. Other gems occur in color-change varieties, including sapphire, spinel. Alexandrite displays a color change dependent upon light, along with strong pleochroism; the gem results from small-scale replacement of aluminium by chromium oxide, responsible for alexandrite's characteristic green to red color change. Alexandrite from the Ural Mountains in Russia is green by red by incandescent light. Other varieties of alexandrite may be yellowish or pink in daylight and a columbine or raspberry red by incandescent light.
The optimum or "ideal" color change would be fine emerald green to fine purplish red, but this is rare. Iridescence is the'play' or'fire' of rainbow-coloured light caused by thin regular structures or layers beneath the surface of a gemstone. Similar to a thin film of oil on water, these layers interfere with the rays of reflected light, reinforcing some colours and cancelling others. Iridescence is seen at its best in precious opal. Schiller, from German for "color play", is the metallic iridescence originating from below the surface of a stone that occurs when light is reflected between layers of minerals, it is seen in moonstone and labradorite and is similar to adularescence and aventurescence
Mohs scale of mineral hardness
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative; the method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is relevant for field geologists, who use the scale to identify minerals using scratch kits; the Mohs scale hardness of minerals can be found in reference sheets. Mohs hardness is useful in milling, it allows assessment of.
The scale is used at electronic manufacturers for testing the resilience of flat panel display components. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly; the samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals; as the hardest known occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5. "Scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye. Materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number.
While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number. The Mohs scale is a purely ordinal scale. For example, corundum is twice as hard as topaz; the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale; the table below incorporates additional substances that may fall between levels: Comparison between hardness and hardness: Mohs hardness of elements is taken from G. V. Samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA, 1968. Cordua, William S. "The Hardness of Minerals and Rocks". Lapidary Digest, c. 1990
Melting point
The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium; the melting point of a substance depends on pressure and is specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point; because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point. For most substances and freezing points are equal. For example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures.
For example, agar melts at 85 °C and solidifies from 31 °C. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances, the freezing point of water is not always the same as the melting point. In the absence of nucleators water can exist as a supercooled liquid down to −48.3 °C before freezing. The chemical element with the highest melting point is tungsten, at 3,414 °C; the often-cited carbon does not melt at ambient pressure but sublimes at about 3,726.85 °C. Tantalum hafnium carbide is a refractory compound with a high melting point of 4215 K. At the other end of the scale, helium does not freeze at all at normal pressure at temperatures arbitrarily close to absolute zero. Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip, revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.
A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window and a simple magnifier. The several grains of a solid are placed in a thin glass tube and immersed in the oil bath; the oil bath is heated and with the aid of the magnifier melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, optical detection is automated; the measurement can be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel online, meaning that the sample is taken from the process and measured automatically; this allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory. For refractory materials the high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees.
The spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source, calibrated as a function of temperature. In this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer. For temperatures above the calibration range of the source, an extrapolation technique must be employed; this extrapolation is accomplished by using Planck's law of radiation. The constants in this equation are not known with sufficient accuracy, causing errors in the extrapolation to become larger at higher temperatures. However, standard techniques have been developed to perform this extrapolation. Consider the case of using gold as the source. In this technique, the current through the filament of the pyrometer is adjusted until the light intensity of the filament matches that of a black-body at the melting point of gold.
This establishes the primary calibration temperature and can be expressed in terms of current through the pyrometer lamp. With the same current setting, the pyrometer is sighted on another black-body at a higher temperature. An absorbing medium of known transmission is inserted between this black-body; the temperature of the black-body is adjusted until a match exists between its intensity and that of the pyrometer filament. The true higher temperature of the black-body is determined from Planck's Law; the absorbing medium is removed and the current through the filament is adjusted to match the filament intensity to that of the black-body. This establishes a second calibration point for the pyrometer; this step is repeated to carry the calibration to hi
Freiberg
Freiberg is a university and mining town in the Free State of Saxony, Germany. It is the administrative centre of Mittelsachsen district, its historic town centre has been placed under heritage conservation and is a chosen site for the proposed UNESCO World Heritage Site known as the Ore Mountain Mining Region. Until 1969, the town was dominated for around 800 years by smelting industries. In recent decades it has restructured into a high technology site in the fields of semiconductor manufacture and solar technology, part of Silicon Saxony; the town lies on the northern declivity of the Ore Mountains, with the majority of the borough west of the Eastern or Freiberger Mulde river. Parts of the town are nestled in the valleys of Goldbach streams, its centre has an altitude of about 412 m above NHN. Its lowest point is on Münzbach on the town boundary at 340 m above NHN. Freiberg lies within a region of old forest clearances, subsequently used by the mining industry which left its mark on the landscape.
The town is surrounded to the north and southwest by woods, in the other directions by fields and meadows. Since the beginning of the 21st century an urbanised area has developed, formed by the towns of Nossen, Roßwein, Großschirma and Brand-Erbisdorf, it has about 75,000 inhabitants. Freiberg is located about 31 kilometres west-southwest of Dresden, about 31 kilometres east-northeast of Chemnitz, about 82 kilometres southeast of Leipzig, about 179 kilometres south of Berlin and about 120 kilometres northwest of Prague. Freiberg lies on a boundary between two variants of the Saxon dialect: the Southeast Meissen dialect to the east and the South Meissen dialect to the west of the town, both belonging to the five Meissen dialects, as well as just north of the border of the dialect region of East Erzgebirgisch; the nucleus of the town, the former forest village of Christiansdorf lies in the valley of the Münzbach stream. The unwalled town centre grew up on the ridge to the west; this means inter alia that the roads radiating outwards east of the old main road axis, some of which run as far as the opposite side of the Münzbach valley, are steep.
The area located east of the main road axis is called Unterstadt, with its lower market or Untermarkt. The western area is the Oberstadt where "Upper Market" is situated; the town centre is surrounded by a green belt running along the old town wall. In the west, this belt, in which the ponds of the Kreuzteichen are set, broadens out into an area like a park. Just north of the town centre, is Freudenstein Castle as well as the remnants of the town wall with several wall towers and Schlüsselteich pond in front of them; the remains of the wall run eastwards, to the Donats Tower. This area is dominated by the historic moat; the southern boundary of the old town is characterised in places by buildings from the Gründerzeit period. The B 101 federal road, here called Wallstraße, flanks the west of the town centre, the B 173, as Schillerstraße and Hornstraße, bounds it to the south. Freiberg's north is dominated by the campus of its University of Technology; the main part of the campus on either side of Leipziger Straße emerged in the 1960s.
Furthermore, the districts of Lossnitz, Lößnitz and Kleinwaltersdorf are found here, extending out to the boundary of the borough. Between Kleinwaltersdorf and Lößnitz is the Nonnenwald wood, east of Leipziger Straße is a trading estate. In the area around Freiberg there are both industrial estates as well as agricultural and recreational areas. Smelting and metalworking firms are based at Muldenhütten and Halsbrücke and paper manufacturers at Weißenborn and Großschirma. Northeast of the town is the recreational area of the Tharandt Forest The town of Großschirma lies north of Freiberg on the B 101 federal road. To the northeast the municipality of Halsbrücke borders on the territory of Freiberg's borough and, to the east, is the municipality of Bobritzsch-Hilbersdorf; the municipality of Weißenborn to the southeast belongs to the Verwaltungsgemeinschaft of Lichtenberg/Erzgebirge. On the B 101 south of Freiberg is the Große Kreisstadt of Brand-Erbisdorf and to the east is the municipality of Oberschöna.
The town was founded in 1186 and has been a centre of the mining industry in the Ore Mountains for centuries. A symbol of that history is the Freiberg University of Mining and Technology just known as the Mining Academy, established in 1765 and the second oldest university of mining and metallurgy in the world. Freiberg has a notable cathedral containing two famous Gottfried Silbermann organs. There are two other organs made by Gottfried Silbermann – one at the St. Peter's Church and the other one at the St. James' Church; the medieval part of Freiberg stands under heritage protection. The river, Freiberger Mulde, flows through the borough of Freiberg, but not the town itself. In 1944, a subcamp of Flossenbürg concentration camp, was built outside the town of Freiberg, it housed including Auschwitz Birkenau. Altogether 50 or so SS women worked in this camp until its evacuation in April 1945; the female survivors e
Cerro de Pasco
Cerro de Pasco is a city in central Peru, located at the top of the Andean mountains. It is the capital of the Pasco region, an important mining center. At 4,330 metres elevation, it is one of the highest cities in the world, the highest or the second highest city with over 50,000 inhabitants, with elevation reaching up to 4,380 m in the Yanacancha area, it is connected by rail to the capital Lima, as far as 300 km. Cerro de Pasco became one of the world's richest silver producing areas after silver was discovered there in 1630, it is still an active mining center. The Spanish mined the rich Cerro de Pasco silver-bearing oxide ore deposits since colonial times. Sulfide minerals are more common in the Atacocha district however. Francisco Uville arranged for steam engines made by Richard Trevithick of Cornwall, England, to be installed in Cerro de Pasco in 1816 to pump water from the mines and allow lower levels to be reached. However, fighting in the Peruvian War of Independence brought production to a halt from 1820 to 1825.
Three major mines in the area include the Machcan and Milpo. SIlver ore occurs in hydrothermal veins or as sulfides and clay minerals replacing the Jurassic Pucara limestone. Porphyry dacite stocks are found intruded near the Atacocha and Milpo mines along the Atacocha Fault. Compania Minera Atacocha started operations at the Atacocha Mine in 1936. Ore minerals include sphalerite. Contamination of the environment by lead and other heavy metals has precipitated a public health crisis in the city, but a 2006 law proposing to evacuate all inhabitants and relocate the city has not yet culminated in concrete action. At 4,330 metres above sea level, Cerro de Pasco has an Alpine tundra climate with the average temperature of the warmest month below the 10 °C ) threshold that would allow for tree growth, giving the countryside its barren appearance; the city is the largest in the world with this classification. Cerro de Pasco has humid and cloudy summers with frequent rainfall and dry, sunny winters with cool to cold temperatures throughout the year.
Snowfall occurs sporadically during any season and is most around dawn. The average annual temperature in Cerro de Pasco is 5.5 °C and the average annual rainfall is 999 mm. Daniel Alcides Carrión Yanacocha Toquepala mine
Fluorite
Fluorite is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals, it crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 4 as Fluorite. Fluorite is a colorful mineral, both in visible and ultraviolet light, the stone has ornamental and lapidary uses. Industrially, fluorite is used as a flux for smelting, in the production of certain glasses and enamels; the purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, the intermediate source of most fluorine-containing fine chemicals. Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes. Fluorite optics are usable in the far-ultraviolet and mid-infrared ranges, where conventional glasses are too absorbent for use; the word fluorite is derived from the Latin verb fluere, meaning to flow.
The mineral is used as a flux in iron smelting to decrease the viscosity of slags. The term flux comes from the Latin adjective fluxus, meaning flowing, slack; the mineral fluorite was termed fluorospar and was first discussed in print in a 1530 work Bermannvs sive de re metallica dialogus, by Georgius Agricola, as a mineral noted for its usefulness as a flux. Agricola, a German scientist with expertise in philology and metallurgy, named fluorspar as a neo-Latinization of the German Flussspat from Fluß and Spat. In 1852, fluorite gave its name to the phenomenon of fluorescence, prominent in fluorites from certain locations, due to certain impurities in the crystal. Fluorite gave the name to its constitutive element fluorine. Presently, the word "fluorspar" is most used for fluorite as the industrial and chemical commodity, while "fluorite" is used mineralogically and in most other senses. In the context of archeology, classical studies, egyptology, the Latin terms murrina and myrrhina refer to fluorite.
In book 37 of his Naturalis Historia, Pliny the Elder describes it as a precious stone with purple and white mottling, whose objects carved from it, the Romans prize. Fluorite crystallises in a cubic motif. Crystal twinning adds complexity to the observed crystal habits. Fluorite has four perfect cleavage planes. Element substitution for the calcium cation includes certain rare earth elements, such as yttrium and cerium. Iron and barium are common impurities; some fluorine may be replaced by the chloride anion. Fluorite is a occurring mineral that occurs globally with significant deposits in over 9,000 areas, it may occur as a vein deposit with metallic minerals, where it forms a part of the gangue and may be associated with galena, barite and calcite. It is a common mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks and as a common minor constituent of dolostone and limestone; the world reserves of fluorite are estimated at 230 million tonnes with the largest deposits being in South Africa and China.
China is leading the world production with about 3 Mt annually, followed by Mexico, Russia, South Africa and Namibia. One of the largest deposits of fluorspar in North America is located in the Burin Peninsula, Canada; the first official recognition of fluorspar in the area was recorded by geologist J. B. Jukes in 1843, he noted an occurrence of "galena" or lead ore and fluoride of lime on the west side of St. Lawrence harbour, it is recorded that interest in the commercial mining of fluorspar began in 1928 with the first ore being extracted in 1933. At Iron Springs Mine, the shafts reached depths of 970 feet. In the St. Lawrence area, the veins are persistent for great lengths and several of them have wide lenses; the area with veins of known workable size comprises about 60 square miles. Cubic crystals up to 20 cm across have been found at Russia; the largest documented single crystal of fluorite was a cube weighing ~ 16 tonnes. Fluorite may be found in mines in Caldoveiro Peak, in Asturias, Spain.
One of the most famous of the older-known localities of fluorite is Castleton in Derbyshire, where, under the name of Derbyshire Blue John, purple-blue fluorite was extracted from several mines or caves. During the 19th century, this attractive fluorite was mined for its ornamental value; the mineral Blue John is now scarce, only a few hundred kilograms are mined each year for ornamental and lapidary use. Mining still takes place in Treak Cliff Cavern. Discovered deposits in China have produced fluorite with coloring and banding similar to the classic Blue John stone. George Gabriel Stokes named the phenomenon of fluorescence from fluorite, in 1852. Many samples of fluorite exhibit fluorescence under ultraviolet light, a property that takes its name from fluorite. Many minerals, as well as other substances, fluoresce. Fluorescence involves the elevation of electron energy levels by quanta of ultraviolet light, followed by the progressive falling back of the electrons into their previous energy state, releasing quanta of visible light in the process.
In fluorite, the visible
Mount Isa Mines
Mount Isa Mines Limited operates the Mount Isa copper, lead and silver mines near Mount Isa, Australia as part of the Glencore group of companies. For a brief period in 1980, MIM was Australia's largest company, it has pioneered several significant mining industry innovations, including the Isa Process copper refining technology, the Isasmelt smelting technology, the IsaMill fine grinding technology, it commercialized the Jameson Cell column flotation technology. In 1923 the orebody containing lead and silver was discovered by the miner John Campbell Miles. Mount Isa Mines Limited was one of three companies founded in 1924 to develop the minerals discovered by Miles, but production did not begin until May 1931; the other two companies were Mount Isa South. These were both acquired by MIM by late 1925; the early years were characterized by the struggle to develop the lead–zinc ore bodies, including the need to finance drilling, metallurgical test work and shaft sinking, there was significant doubt that Miles' discovery would amount to much.
However, by the end of 1928, the drilling had allowed an estimate of reserves of 21.2 million tons, which were at the time the largest in Australian history, rose to an estimate of 32 million tons in 1930. The cost of developing the Mount Isa ore body was so high that the owners had to turn to ASARCO to obtain sufficient finance to bring the operation into production; the project was running behind schedule and over budget, which resulted in ASARCO sending its own man, Julius Kruttschnitt II, to take charge. Kruttschnitt arrived in 1930 to find that bills were going unpaid because there was no money to pay them, the shafts were flooding, the construction of the surface plants was months behind schedule; when mining commenced in 1931, the mine was mechanized to an extent not seen in Australia, with mechanized drilling and mechanical shovels rather than "hammer and tap" hand drilling and hand shovels. The initial mine production was 660,000 tonnes per year of ore and stayed at about this level until 1953.
After the first ore had been mined and processed, the Mount Isa operations struggled. The smelter required a third blast furnace and additional sintering machines; the recovery of valuable minerals in the concentrator was less than expected, the metal prices were depressed by the Great Depression of the 1930s. The poor recoveries were found to be caused by the unusually fine nature of the mineral grains in the Mount Isa ore. While the metal prices recovered as the Depression passed, the fine mineral grains were to plague the Mount Isa lead–zinc operations for the rest of their days. By June 1933, the debt owed by MIM to creditors around the world, ₤2.88 million, was equal to 15% of all income tax paid in Australia in 1932. It was not until the 1936–1937 financial year that MIM made its first profit and the company could begin to pay down its burden of debt. However, the outbreak of The Second World War was not kind to MIM, because it could no longer find markets for all its production, the price of lead did not increase as it had during the First World War.
While some copper mineralization had been discovered during drilling in the late 1920s, the major find did not come until 1930, when drilling to explore the lead–zinc ore body passed through 38 meters of copper mineralization with an average grade of 4.3% copper. While this was a good grade, MIM did not have the financial resources to develop the copper, it was not until global copper prices increased in 1937 that there was an incentive for further copper exploration; these efforts were unsuccessful, but yielded fruit in 1940 and 1941. However, it was not until 1941–1942 that mining of the No. 7 level of the Black Star lead-zinc ore body allowed the existence of an economic copper deposit to be established. MIM was still not in a position to mine the copper, because it had stockpiles of lead bullion and zinc concentrate that could not be sold due to the war. However, the Australian government needed copper for its war effort and lent MIM ₤50,000 to allow the mining to proceed. Further drilling expanded the copper reserves and MIM decided to switch from lead to copper production.
The lead–zinc concentrator could treat the copper ore with little modification, but the lead smelter required the addition of second-hand equipment lying idle at the Kuridala, Mount Cuthbert and Mount Elliott mines. Lead smelting ceased on 9 April 1943 and sintering of copper concentrate commenced on the same day. While the copper had the potential to be more profitable, MIM's run of bad luck did not end then: the Australian Government's Department of Supply and Shipping decided that it no longer needed MIM's copper and recommended returning production to lead and zinc as from January 1944, without compensation for the expense of converting the operations to copper production. After much discussion between MIM and the Australian government, MIM was permitted to continue to produce copper until six months after the end of the Pacific War, the last copper was produced on 2 May 1946 and lead production resumed at a time of rising lead prices. In 1947, MIM paid its first dividend, signaling an end to its early troubles, after 16 years of continuous production and 23 years after the company's formation.
That same year, exploration began north of the Mount Isa ore bodies, in an area that became the Hilton mine and, following the discovery of an outcrop of rocks similar to the host rocks of the Mount Isa ore bodies, diamond drilling began in August 1948. That first drill hole intersected a small amount of zinc mineralization. From until 1957, a significant drilling program was undertaken and by 1950, the Hilton o
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