Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit. Ore is extracted from the earth through mining and treated or refined, often via smelting, to extract the valuable metals or minerals. The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining, and is therefore considered an ore.
Smelting is a process of applying heat to ore in order to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind. The reducing agent is commonly a fossil fuel source of carbon, such as coke—or, in earlier times, charcoal. The oxygen in the ore binds to carbon at high temperatures due to the lower potential energy of the bonds in carbon dioxide. Smelting most prominently takes place in a blast furnace to produce pig iron, which is converted into steel.
Chalcopyrite ( KAL-kə-PY-ryte, -koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.
Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system (pseudo-cubic).
Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains the most important source of tin today.
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Skarns or tactites are hard, coarse-grained metamorphic rocks that form by a process called metasomatism. Skarns tend to be rich in calcium-magnesium-iron-manganese-aluminium silicate minerals, which are also referred to as calc-silicate minerals. These minerals form as a result of alteration which occurs when hydrothermal fluids interact with a protolith of either igneous or sedimentary origin. In many cases, skarns are associated with the intrusion of a granitic pluton found in and around faults or shear zones that intrude into a carbonate layer composed of either dolomite or limestone. Skarns can form by regional, or contact metamorphism and therefore form in relatively high temperature environments. The hydrothermal fluids associated with the metasomatic processes can originate from either magmatic, metamorphic, meteoric, marine, or even a mix of these. The resulting skarn may consist of a variety of different minerals which are highly dependent on both the original composition of the hydrothermal fluid and the original composition of the protolith.
Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper.
Tennantite is a copper arsenic sulfosalt mineral with an ideal formula Cu12As4S13. Due to variable substitution of the copper by iron and zinc the formula is Cu6[Cu4(Fe,Zn)2]As4S13. It is gray-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedrite (Cu12Sb4S13) has antimony substituting for arsenic and the two form a solid solution series. The two have very similar properties and is often difficult to distinguish between tennantite and tetrahedrite. Iron, zinc, and silver substitute up to about 15% for the copper site.
Cobaltite is a sulfide mineral composed of cobalt, arsenic, and sulfur, CoAsS. Its impurities may contain up to 10% iron and variable amounts of nickel. Structurally, it resembles pyrite (FeS2) with one of the sulfur atoms replaced by an arsenic atom.
Sperrylite is a platinum arsenide mineral with the chemical formula PtAs2 and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in addition to massive and reniform habits. It has a Mohs hardness of 6 - 7 and a very high specific gravity of 10.6.
Various theories of ore genesis explain how the various types of mineral deposits form within the Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
Mining in Cornwall and Devon, in the southwest of England, began in the early Bronze Age, around 2150 BC. Tin, and later copper, were the most commonly extracted metals. Some tin mining continued long after the mining of other metals had become unprofitable, but ended in the late 20th century. In 2021, it was announced that a new mine was extracting battery-grade lithium carbonate, more than 20 years after the closure of the last South Crofty tin mine in Cornwall in 1998.
A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, molybdenum, nickel, niobium, rhenium, selenium, tantalum, tellurium, tin, titanium, tungsten, vanadium, and zinc, as well as the gold group and the platinum group. Among the alloys found in native state have been brass, bronze, pewter, German silver, osmiridium, electrum, white gold, silver-mercury amalgam, and gold-mercury amalgam.
Cubanite is a copper iron sulfide mineral that commonly occurs as a minor alteration mineral in magmatic sulfide deposits. It has the chemical formula CuFe2S3 and when found, it has a bronze to brass-yellow appearance. On the Mohs hardness scale, cubanite falls between 3.5 and 4 and has a orthorhombic crystal system. Cubanite is chemically similar to chalcopyrite, however it is the less common copper iron sulfide mineral due to crystallization requirements.
Tin is an essential metal in the creation of tin bronzes, and its acquisition was an important part of ancient cultures from the Bronze Age onward. Its use began in the Middle East and the Balkans around 3000 BC. Tin is a relatively rare element in the Earth's crust, with about two parts per million (ppm), compared to iron with 50,000 ppm, copper with 70 ppm, lead with 16 ppm, arsenic with 5 ppm, silver with 0.1 ppm, and gold with 0.005 ppm. Ancient sources of tin were therefore rare, and the metal usually had to be traded over very long distances to meet demand in areas which lacked tin deposits.
Stannoidite is a sulfide mineral composed of five chemical elements: copper, iron, zinc, tin and sulfur. Its name originates from Latin stannum (tin) and Greek eides. The mineral is found in hydrothermal Cu-Sn deposits.
Kësterite is a sulfide mineral with a chemical formula of Cu2(Zn,Fe)SnS4. In its lattice structure, zinc and iron atoms share the same lattice sites. Kesterite is the Zn-rich variety whereas the Zn-poor form is called ferrokesterite or stannite. Owing to their similarity, kesterite is sometimes called isostannite. The synthetic form of kesterite is abbreviated as CZTS. The name kesterite is sometimes extended to include this synthetic material and also CZTSe, which contains selenium instead of sulfur.
Tin mining began early in the Bronze Age, as bronze is a copper-tin alloy. Tin is a relatively rare element in the Earth's crust, with approximately 2 ppm, compared to iron with 50,000 ppm.
Mawsonite is a brownish orange sulfosalt mineral, containing copper, iron, tin, and sulfur: Cu6Fe2SnS8.
