Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties. It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure. Bronze is an alloy containing copper, but instead of zinc it has tin. Both bronze and brass may include small proportions of a range of other elements including arsenic, phosphorus, aluminium and silicon; the distinction is historical. Modern practice in museums and archaeology avoids both terms for historical objects in favour of the all-embracing "copper alloy". Brass is used for decoration for its bright gold-like appearance, it is used in zippers. Brass is used in situations in which it is important that sparks not be struck, such as in fittings and tools used near flammable or explosive materials. Brass has higher malleability than zinc; the low melting point of brass and its flow characteristics make it a easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.
The density of brass is 8.4 to 8.73 grams per cubic centimetre. Today 90% of all brass alloys are recycled; because brass is not ferromagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet. Brass scrap is transported to the foundry where it is melted and recast into billets. Billets are extruded into the desired form and size; the general softness of brass means that it can be machined without the use of cutting fluid, though there are exceptions to this. Aluminium makes brass more corrosion-resistant. Aluminium causes a beneficial hard layer of aluminium oxide to be formed on the surface, thin and self-healing. Tin has a similar effect and finds its use in seawater applications. Combinations of iron, aluminium and manganese make brass wear and tear resistant. To enhance the machinability of brass, lead is added in concentrations of around 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting.
The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface; these effects can lead to significant lead leaching from brasses of comparatively low lead content. In October 1999 the California State Attorney General sued 13 key manufacturers and distributors over lead content. In laboratory tests, state researchers found the average brass key, new or old, exceeded the California Proposition 65 limits by an average factor of 19, assuming handling twice a day. In April 2001 manufacturers agreed to reduce lead content to 1.5%, or face a requirement to warn consumers about lead content. Keys plated with other metals are not affected by the settlement, may continue to use brass alloys with higher percentage of lead content. In California, lead-free materials must be used for "each component that comes into contact with the wetted surface of pipes and pipe fittings, plumbing fittings and fixtures."
On January 1, 2010, the maximum amount of lead in "lead-free brass" in California was reduced from 4% to 0.25% lead. The so-called dezincification resistant brasses, sometimes referred to as CR brasses, are used where there is a large corrosion risk and where normal brasses do not meet the standards. Applications with high water temperatures, chlorides present, or deviating water qualities play a role. DZR-brass is excellent in water boiler systems; this brass alloy must be produced with great care, with special attention placed on a balanced composition and proper production temperatures and parameters to avoid long-term failures. The high malleability and workability good resistance to corrosion, traditionally attributed acoustic properties of brass, have made it the usual metal of choice for construction of musical instruments whose acoustic resonators consist of long narrow tubing folded or coiled for compactness. Collectively known as brass instruments, these include the trombone, trumpet, baritone horn, tenor horn, French horn, many other "horns", many in variously-sized families, such as the saxhorns.
Other wind instruments may be constructed of brass or other metals, indeed most modern student-model flutes and piccolos are made of some variety of brass a cupronickel alloy similar to nickel silver/German silver. Clarinets low clarinets such as the contrabass and subcontrabass, are sometimes made of metal because of limited supplies of the dense, fine-grained tropical hardwoods traditionally preferred for smaller woodwinds. For the same reason, some low clarinets and contrabassoons feature a hybrid construction, with long, straight sections of wood, curved joints, and/or bell of metal; the use of metal avoids the risks of exposing wooden instruments to changes in temperature or humid
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric
An alloy is a combination of metals and of a metal or another element. Alloys are defined by a metallic bonding character. An alloy may be a mixture of metallic phases. Intermetallic compounds are alloys with a defined crystal structure. Zintl phases are sometimes considered alloys depending on bond types. Alloys are used in a wide variety of applications. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties. In other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel, brass, duralumin and amalgams; the alloy constituents are measured by mass percentage for practical applications, in atomic fraction for basic science studies. Alloys are classified as substitutional or interstitial alloys, depending on the atomic arrangement that forms the alloy, they can be heterogeneous or intermetallic. An alloy is a mixture of chemical elements, which forms an impure substance that retains the characteristics of a metal.
An alloy is distinct from an impure metal in that, with an alloy, the added elements are well controlled to produce desirable properties, while impure metals such as wrought iron are less controlled, but are considered useful. Alloys are made by mixing two or more elements, at least one of, a metal; this is called the primary metal or the base metal, the name of this metal may be the name of the alloy. The other constituents may or may not be metals but, when mixed with the molten base, they will be soluble and dissolve into the mixture; the mechanical properties of alloys will be quite different from those of its individual constituents. A metal, very soft, such as aluminium, can be altered by alloying it with another soft metal, such as copper. Although both metals are soft and ductile, the resulting aluminium alloy will have much greater strength. Adding a small amount of non-metallic carbon to iron trades its great ductility for the greater strength of an alloy called steel. Due to its very-high strength, but still substantial toughness, its ability to be altered by heat treatment, steel is one of the most useful and common alloys in modern use.
By adding chromium to steel, its resistance to corrosion can be enhanced, creating stainless steel, while adding silicon will alter its electrical characteristics, producing silicon steel. Like oil and water, a molten metal may not always mix with another element. For example, pure iron is completely insoluble with copper; when the constituents are soluble, each will have a saturation point, beyond which no more of the constituent can be added. Iron, for example, can hold a maximum of 6.67% carbon. Although the elements of an alloy must be soluble in the liquid state, they may not always be soluble in the solid state. If the metals remain soluble when solid, the alloy forms a solid solution, becoming a homogeneous structure consisting of identical crystals, called a phase. If as the mixture cools the constituents become insoluble, they may separate to form two or more different types of crystals, creating a heterogeneous microstructure of different phases, some with more of one constituent than the other phase has.
However, in other alloys, the insoluble elements may not separate until after crystallization occurs. If cooled quickly, they first crystallize as a homogeneous phase, but they are supersaturated with the secondary constituents; as time passes, the atoms of these supersaturated alloys can separate from the crystal lattice, becoming more stable, form a second phase that serve to reinforce the crystals internally. Some alloys, such as electrum, an alloy consisting of silver and gold, occur naturally. Meteorites are sometimes made of occurring alloys of iron and nickel, but are not native to the Earth. One of the first alloys made by humans was bronze, a mixture of the metals tin and copper. Bronze was an useful alloy to the ancients, because it is much stronger and harder than either of its components. Steel was another common alloy. However, in ancient times, it could only be created as an accidental byproduct from the heating of iron ore in fires during the manufacture of iron. Other ancient alloys include pewter and pig iron.
In the modern age, steel can be created in many forms. Carbon steel can be made by varying only the carbon content, producing soft alloys like mild steel or hard alloys like spring steel. Alloy steels can be made by adding other elements, such as chromium, vanadium or nickel, resulting in alloys such as high-speed steel or tool steel. Small amounts of manganese are alloyed with most modern steels because of its ability to remove unwanted impurities, like phosphorus and oxygen, which can have detrimental effects on the alloy. However, most alloys were not created until the 1900s, such as various aluminium, titanium and magnesium alloys; some modern superalloys, such as incoloy and hastelloy, may consist of a multitude of different elements. As a noun, the term alloy is used to describe a mixture of atoms in which the primary constituent is a metal; when used as a verb, the term refers to the act of mixing a metal with other elements. The primary metal is called the matrix, or the solvent; the secondary constituents are called s
Silver is a chemical element with symbol Ag and atomic number 47. A soft, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, reflectivity of any metal; the metal is found in the Earth's crust in the pure, free elemental form, as an alloy with gold and other metals, in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold and zinc refining. Silver has long been valued as a precious metal. Silver metal is used in many bullion coins, sometimes alongside gold: while it is more abundant than gold, it is much less abundant as a native metal, its purity is measured on a per-mille basis. As one of the seven metals of antiquity, silver has had an enduring role in most human cultures. Other than in currency and as an investment medium, silver is used in solar panels, water filtration, ornaments, high-value tableware and utensils, in electrical contacts and conductors, in specialized mirrors, window coatings, in catalysis of chemical reactions, as a colorant in stained glass and in specialised confectionery.
Its compounds are used in X-ray film. Dilute solutions of silver nitrate and other silver compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings and other medical instruments. Silver is similar in its physical and chemical properties to its two vertical neighbours in group 11 of the periodic table and gold, its 47 electrons are arranged in the configuration 4d105s1 to copper and gold. This distinctive electron configuration, with a single electron in the highest occupied s subshell over a filled d subshell, accounts for many of the singular properties of metallic silver. Silver is an soft and malleable transition metal, though it is less malleable than gold. Silver crystallizes in a face-centered cubic lattice with bulk coordination number 12, where only the single 5s electron is delocalized to copper and gold. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are weak; this observation explains the low high ductility of single crystals of silver.
Silver has a brilliant white metallic luster that can take a high polish, and, so characteristic that the name of the metal itself has become a colour name. Unlike copper and gold, the energy required to excite an electron from the filled d band to the s-p conduction band in silver is large enough that it no longer corresponds to absorption in the visible region of the spectrum, but rather in the ultraviolet. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm. At wavelengths shorter than 450 nm, silver's reflectivity is inferior to that of aluminium and drops to zero near 310 nm. High electrical and thermal conductivity is common to the elements in group 11, because their single s electron is free and does not interact with the filled d subshell, as such interactions lower electron mobility; the electrical conductivity of silver is the greatest of all metals, greater than copper, but it is not used for this property because of the higher cost.
An exception is in radio-frequency engineering at VHF and higher frequencies where silver plating improves electrical conductivity because those currents tend to flow on the surface of conductors rather than through the interior. During World War II in the US, 13540 tons of silver were used in electromagnets for enriching uranium because of the wartime shortage of copper. Pure silver has the highest thermal conductivity of any metal, although the conductivity of carbon and superfluid helium-4 are higher. Silver has the lowest contact resistance of any metal. Silver forms alloys with copper and gold, as well as zinc. Zinc-silver alloys with low zinc concentration may be considered as face-centred cubic solid solutions of zinc in silver, as the structure of the silver is unchanged while the electron concentration rises as more zinc is added. Increasing the electron concentration further leads to body-centred cubic, complex cubic, hexagonal close-packed phases. Occurring silver is composed of two stable isotopes, 107Ag and 109Ag, with 107Ag being more abundant.
This equal abundance is rare in the periodic table. The atomic weight is 107.8682 u. Both isotopes of silver are produced in stars via the s-process, as well as in supernovas via the r-process. Twenty-eight radioisotopes have been characterized, the most stable being 105Ag with a half-life of 41.29 days, 111Ag with a half-life of 7.45 days, 112Ag with a half-life of 3.13 hours. Silver has numerous nuclear isomers, the most stable being 108mAg, 110mAg and 106mAg. All of the remaining radioactive isotopes have half-lives of less than an hour, the majority of these have half-lives of less than three minutes. Isotopes of silver range in relative atomic mass from 92.950 u
Orichalcum or aurichalcum is a metal mentioned in several ancient writings, including the story of Atlantis in the Critias of Plato. Within the dialogue, Critias claims that orichalcum had been considered second only to gold in value and had been found and mined in many parts of Atlantis in ancient times, but that by Critias' own time orichalcum was known only by name. Orichalcum may have been a noble metal such as platinum, as it was supposed to be mined, or one type of bronze or brass or some other metal alloy. In 2015, metal ingots were found in an ancient shipwreck in Gela, which were made of an alloy consisting of copper and small percentages of nickel and iron. In numismatics, orichalcum is the golden-colored bronze alloy used by the Roman Empire for their sestertius and dupondius coins; the name is derived from the Greek ὀρείχαλκος, meaning "mountain copper". The Romans transliterated "orichalcum" as "aurichalcum", thought to mean "gold copper", it is known from the writings of Cicero that the metal which they called orichalcum resembled gold in color but had a much lower value.
In Virgil's Aeneid, the breastplate of Turnus is described as "stiff with gold and white orichalc". Orichalcum has been held to be either a gold-copper alloy, a copper-tin or copper-zinc brass, or a metal or metallic alloy no longer known. In years, "orichalcum" was used to describe the sulfide mineral chalcopyrite and to describe brass. However, these usages are difficult to reconcile with the claims of Plato's Critias, who states that the metal was "only a name" by his time, while brass and chalcopyrite were important in the time of Plato, as they still are today. Joseph Needham notes that 18th century Bishop Richard Watson, a professor of chemistry, wrote of an ancient idea that there were "two sorts of brass or orichalcum". Needham suggests that the Greeks may not have known how orichalcum was made, that they might have had an imitation of the original. In 2015, 39 ingots believed to be orichalcum were discovered in a sunken vessel on the coasts of Gela in Sicily which have tentatively been dated at 2,600 years old.
They were analyzed with X-ray fluorescence by Dario Panetta of Technologies for Quality and turned out to be an alloy consisting of 75-80 percent copper, 15-20 percent zinc, smaller percentages of nickel and iron. Orichalcum is first mentioned in the 7th century BC by Hesiod, in the Homeric hymn dedicated to Aphrodite, dated to the 630s. According to the Critias of Plato, the three outer walls of the Temple to Poseidon and Cleito on Atlantis were clad with brass and the third outer wall, which encompassed the whole citadel, "flashed with the red light of orichalcum"; the interior walls and floors of the temple were covered in orichalcum, the roof was variegated with gold and orichalcum. In the center of the temple stood a pillar of orichalcum, on which the laws of Poseidon and records of the first son princes of Poseidon were inscribed. Pliny the Elder points out. Pseudo-Aristotle in De mirabilibus auscultationibus describes a type of copper, "very shiny and white, not because there is tin mixed with it, but because some earth is combined and molten with it."
This might be a reference to orichalcum obtained during the smelting of copper with the addition of "cadmia", a kind of earth found on the shores of the Black Sea, attributed to be zinc oxide. In numismatics, the term "orichalcum" is used to refer to the golden-colored bronze alloy used for the sestertius and dupondius coins, it is considered more valuable than copper. Media related to Orichalcum coins at Wikimedia Commons
Aegina is one of the Saronic Islands of Greece in the Saronic Gulf, 27 kilometres from Athens. Tradition derives the name from Aegina, the mother of the hero Aeacus, born on the island and became its king. During ancient times Aegina was a rival of the great sea power of the era; the municipality of Aegina consists of the island of a few offshore islets. It is part of Attica region; the municipality is subdivided into the following five communities: Kypseli Mesagros Perdika Vathy The capital is the town of Aegina, situated at the northwestern end of the island. Due to its proximity to Athens, it is a popular vacation place during the summer months, with quite a few Athenians owning second houses on the island; the province of Aegina was one of the provinces of the Piraeus Prefecture. Its territory corresponded with that of the current municipalities Agkistri, it was abolished in 2006. Aegina is triangular in shape 15 km from east to west and 10 km from north to south, with an area of 87.41 km2. An extinct volcano constitutes two-thirds of Aegina.
The northern and western sides consist of stony but fertile plains, which are well cultivated and produce luxuriant crops of grain, with some cotton, almonds and figs, but the most characteristic crop of Aegina today is pistachio. Economically, the sponge fisheries are of notable importance; the southern volcanic part of the island is rugged and mountainous, barren. Its highest rise is the conical Mount Oros in the south, the Panhellenian ridge stretches northward with narrow fertile valleys on either side; the beaches are a popular tourist attraction. Hydrofoil ferries from Piraeus take only forty minutes to reach Aegina. There are regular bus services from Aegina town to destinations throughout the island such as Agia Marina. Portes is a fishing village on the east coast. Aegina, according to Herodotus, was a colony of Epidaurus, to which state it was subject, its placement between Attica and the Peloponnesus made it a site of trade earlier, its earliest inhabitants came from Asia Minor. Minoan ceramics have been found in contexts of c. 2000 BC.
The famous Aegina Treasure, now in the British Museum is estimated to date between 1700 and 1500 BC. The discovery on the island of a number of gold ornaments belonging to the last period of Mycenaean art suggests that Mycenaean culture existed in Aegina for some generations after the Dorian conquest of Argos and Lacedaemon, it is probable that the island was not doricised before the 9th century BC. One of the earliest historical facts is its membership in the Amphictyony or League of Calauria, attested around the 8th century BC; this ostensibly religious league included—besides Aegina—Athens, the Minyan Orchomenos, Hermione and Prasiae. It was an organisation of city-states that were still Mycenaean, for the purpose of suppressing piracy in the Aegean that began as a result of the decay of the naval supremacy of the Mycenaean princes. Aegina seems to have belonged to the Eretrian league during the Lelantine War, its early history reveals. It is stated on the authority of Ephorus, that Pheidon of Argos established a mint in Aegina, the first city-state to issue coins in Europe, the Aeginetic stater.
One stamped stater can be seen in the Bibliothèque Nationale of Paris. It is an electrum stater of a turtle, an animal sacred to Aphrodite, struck at Aegina that dates from 700 BC. Therefore, it is thought that the Aeginetes, within 30 or 40 years of the invention of coinage in Asia Minor by the Ionian Greeks or the Lydians, might have been the ones to introduce coinage to the Western world; the fact that the Aeginetic standard of weights and measures was one of the two standards in general use in the Greek world is sufficient evidence of the early commercial importance of the island. The Aeginetic weight standard of about 12.3 grams was adopted in the Greek world during the 7th century BC. The Aeginetic stater was divided into three drachmae of 4.1 grams of silver. Staters depicting a sea-turtle were struck up to the end of the 5th century BC. Following the end of the Peloponnesian War, 404 BC, it was replaced by the land tortoise. During the naval expansion of Aegina during the Archaic Period, Kydonia was an ideal maritime stop for Aegina's fleet on its way to other Mediterranean ports controlled by the emerging sea-power Aegina.
During the next century Aegina was one of the three principal states trading at the emporium of Naucratis in Egypt, it was the only Greek state near Europe that had a share in this factory. At the beginning of the 5th century BC it seems to have been an entrepôt of the Pontic grain trade, which, at a date, became an Athenian monopoly. Unlike the other commercial states of the 7th and 6th centuries BC, such as Corinth, Chalcis and Miletus, Aegina did not found any colonies; the settlements to which Strabo refers cannot be regarded as any real exceptions to this statement. The known history of Aegina is exclusively a
Tumbaga is the name for a non-specific alloy of gold and copper given by Spanish Conquistadors to metals composed of these elements found in widespread use in pre-Columbian Mesoamerica and South America. The term is believed to be a borrowing from Malay tembaga, meaning "copper" or "brass", which in turn is from Prakrit. Tumbaga is an alloy composed of gold and copper, it has a lower melting point than gold or copper alone. It maintains malleability after being pounded. Tumbaga can be treated like citric acid, to dissolve copper off the surface. What remains is a shiny layer of nearly pure gold on top of a harder, more durable copper-gold alloy sheet; this process is referred to as depletion gilding. Tumbaga was used by the pre-Columban cultures of Central America to make religious objects. Like most gold alloys, tumbaga was versatile and could be cast, hammered, soldered, plated, annealed, engraved and inlaid; the proportion of gold to copper in artifacts varies widely. Some tumbaga has been found to be composed of metals besides gold and copper, up to 18% of the total mass of the tumbaga.
Tumbaga objects were made using a combination of the lost wax technique and depletion gilding. An alloy of varying proportions of copper and gold was cast. After removal it was burned, turning surface copper into copper oxide, mechanically removed The object was placed in an oxidizing solution composed of sodium chloride and ferric sulfate; this dissolved the silver from the surface. When viewed through a microscope, voids appear where the silver had been. In 1992 200 silver "tumbaga" bars were recovered in wreckage off Grand Bahama Island, they were composed of silver and gold plundered by the Spaniards during the conquests of Cortés and hastily melted into bars of tumbaga for transport across the Atlantic. Such bars were melted back into their constituent metals in Spain. Shipwreck recovered right after the conquest of Cortés with tumbaga gold bars The "Tumbaga" Saga: Treasure of the Conquistadors. Book about Tumbaga Bars The Art of Precolumbian Gold: The Jan Mitchell Collection, an exhibition catalog from The Metropolitan Museum of Art, which contains material on Tumbaga