Precious metal

Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Precious metals, particularly the noble metals, are more corrosion resistant and less chemically reactive than most elements. They are usually ductile and have a high lustre. Historically, precious metals were important as currency but they are now regarded mainly as investment and industrial raw materials. Gold, silver, platinum, and palladium each have an ISO 4217 currency code.

The best known precious metals are the precious coinage metals, which are gold and silver. Although both have industrial uses, they are better known for their uses in art, jewelry, and coinage. Other precious metals include the platinum group metals: ruthenium, rhodium, palladium, osmium, iridium, and platinum, of which platinum is the most widely traded. The demand for precious metals is driven not only by their practical use but also by their role as investments and a store of value. Historically, precious metals have commanded much higher prices than common industrial metals.

Taxonomy

Gold (chemical number 79), silver (chemical number 47), platinum (chemical number 78), and palladium (chemical number 46) each have an ISO 4217 code. Other precious metals are ruthenium (chemical number 44), rhodium (chemical number 45), osmium (chemical number 76), and iridium (chemical number 77) .

In the Mendeleev 's periodic table of elements you will notice how they are all close together and all belong to the IUPAC group VIII, except silver and gold which belong to the IUPAC group IB (which is also immediately after group VIII) .

Uses

Precious metals have many industrial applications. In particular, electronics uses platinum, palladium, rhodium, gold, and silver. Precious metals are also essential for the medical sector (prosthetics).

Gold and silver, and sometimes other precious metals, are often seen as defensive assets against both inflation and economic downturn. Silver coins have become popular with collectors due to their relative affordability, and, unlike most gold and platinum issues which are valued based upon the markets, silver issues are more often valued as collectibles, at far higher than their bullion value.

Platinum and palladium are key catalysts in hydrogenation reactions and emission-reducing catalytic converters, while gold is used in oxidation reactions and nanotechnology due to its stability. Platinum group metals(PGMs) have been used in the production of sulfuric and nitric acid for centuries. Additionally, gold and silver nanoparticles are used in biosensors and solar cells, underscoring their value in sustainable technologies.

In jewelry, precious metals are usually gold (Au), silver (Ag), platinum (Pt), rhodium (Rh), and palladium (Pd)—in some cases, ruthenium (Ru), osmium (Os), and iridium (Ir) are also often included. It is precisely because of this low tendency to react that they have been used in jewelry since ancient times.

One of the fundamental characteristics of a piece of jewelry is its durability; for this reason, the finest materials available are used. Sometimes, precious metals don't possess all the mechanical qualities that would be desirable for use in goldsmithing, jewelry, or costume jewelry, which is why alloys are used.

The production of these metals by extraction from the natural environment is no longer sufficient to meet global consumption needs. For example, for gold, whose production has been declining since 2001, it is estimated that 10 to 20% of consumption comes from recycling.

Bullion

A metal is deemed to be precious if it is rare. The discovery of new sources of ore or improvements in mining or refining processes may cause the value of a precious metal to diminish. The status of a "precious" metal can also be determined by high demand or market value. Precious metals in bulk form are known as bullion and are traded on commodity markets. Bullion metals may be cast into ingots or minted into coins. The defining attribute of bullion is that it is valued by its mass and purity rather than by a face value as money.

Purity and mass

The level of purity varies from issue to issue. "Three nines" (99.9%) purity is common. The purest mass-produced bullion coins are in the Canadian Gold Maple Leaf series, which go up to 99.999% purity. A 100% pure bullion is nearly impossible: as the percentage of impurities diminishes, it becomes progressively more difficult to purify the metal further. Historically, coins had a certain amount of weight of alloy, with the purity a local standard. The Krugerrand is the first modern example of measuring in "pure gold": it should contain at least 12⁄11 ounces of at least 11⁄12 pure gold. Other bullion coins (for example the British Sovereign) show neither the purity nor the fine-gold weight on the coin but are recognized and consistent in their composition. Many coins historically showed a denomination in currency (example: American double eagle: $20).

Coinage

Many nations mint bullion coins. Although nominally issued as legal tender, these coins' face value as currency is far below their value as bullion. For instance, Canada mints a gold bullion coin (the Gold Maple Leaf) at a face value of $50 containing one troy ounce (31.1035 g) of gold, as of January 2022. The USD to CAD exchange rate averaged 1.129 in July 2009 according to OANDA Historical Exchange Rates. Although the exact moment that the $1,075 figure[clarification needed] was determined is unknown, it may be considered a reasonable value for the time. Bullion coins' minting by national governments gives them some numismatic value in addition to their bullion value, as well as certifying their purity.

One of the largest bullion coins in the world was the 10,000-dollar Australian Gold Nugget coin minted in Australia, which consists of a full kilogram of 99.9% pure gold. In 2012, the Perth Mint produced a 1-tonne coin of 99.99% pure gold with a face value of $1 million AUD, making it the largest minted coin in the world with a gold value of around $50 million AUD. China has produced coins in very limited quantities (less than 20 pieces minted) that exceed 8 kilograms (260 ozt) of gold. Austria has minted a coin containing 31 kg of gold (the Vienna Philharmonic Coin minted in 2004 with a face value of 100,000 euro). As a stunt to publicise the 99.999% pure one-ounce Canadian Gold Maple Leaf series, in 2007 the Royal Canadian Mint made a 100 kg 99.999% gold coin, with a face value of $1 million, and now manufactures them to order, but at a substantial premium over the market value of the gold.

The Reserve Bank of Zimbabwe mints the gold Mosi-oa-Tunya (coin) which is recognized as legal tender at the market value for its gold content.

Types of precious metals

Rhodium

Rhodium is the chemical element with atomic number 45 and its symbol is Rh. It is a rare, hard, silvery-white transition metal. It is found in platinum ores and, in alloy with it, is used as a catalyst.

Rhodium is a white metal similar to aluminum. It can be easily alloyed with other metals. Its use in jewelry is limited to rhodium plating applied to white gold or platinum. White gold is usually electroplated with an outer layer of rhodium 0.05 to 0.5 micrometers thick. Because of this thin layer, scratches in this layer are common. This causes oxidation and further weakens the rhodium layer. Ideally, a 2.0 μm layer is recommended for longer durability. White gold jewelry with rhodium can be replated in some jewelry stores.

Platinum

Platinum is a metal, it is the chemical element with atomic number 78 and its symbol is Pt. It is a transition metal, malleable, ductile (it is the most ductile metal after gold and silver) of white-grey colour.

Platinum, a lustrous, white/gray precious metal, is rarely used in jewelry today due to its high price and the limited number of specialized jewelers skilled in working with it. A few years ago, it was used to set high-value stones. It is very ductile, surpassed only by gold and silver, and can be drawn into very thin wires or sheets.

It's quite soft and can be easily scratched if it hasn't been previously laminated. If alloyed with gold, it becomes brittle. Palladium hardens it relatively, while iridium hardens it in a medium way.

Gold

750-thousandths gold is an alloy of 750 parts (3/4) of fine gold with 250 parts (1/4) of another metal or metals (silver, copper, etc.) to give it mechanical qualities that pure gold does not have, such as rigidity, strength, and color. This percentage of gold in the alloy is also known as 18- karat gold.

The colors of gold

The formulas presented below are for 18-carat gold.  

Yellow gold: Alloy that has, for every 1000 g of it, 750 g of fine gold, 125 g of fine silver and 125 g of copper.

Red gold: Here the proportions are 750 g of fine gold and 250 g of copper.

Rose gold: The content of 1000 g contains 750 g of fine gold, 50 g of fine silver and 200 g of copper.

White gold: For every 1000 g of white gold, there is 750 g of fine gold and 100 to 160 g of palladium. The remainder is fine silver. Palladium can be substituted with nickel.

Gray gold: In 1000 g of gray gold, there are 750 g of fine gold and about 150 g of nickel. The remainder is copper.

Green gold: In 1000 g of green gold there are 750 g of fine gold and 250 g of silver.

Blue gold: In 1000 g of blue gold there are 750 g of fine gold and 250 g of iron.

Ruthenium

Ruthenium is the chemical element with atomic number 44 and its symbol is Ru. It is a rare transition metal of the iron group, it is found in platinum ores and in alloy with it it is used as a catalyst.

Iridium

Iridium is the chemical element with atomic number 77 and its symbol is Ir. It is a silvery-white, very hard transition metal belonging to the platinum group. It occurs naturally in alloy with osmium and is used in the production of metal alloys intended to work at high temperatures and under conditions of high wear.

Osmium

Osmium is the chemical element with atomic number 76 and its symbol is Os. It is a transition metal of the platinum period: it is a hard metal, of a blue-gray or blackish blue color and is used in some alloys with platinum and iridium. It is found in nature in alloy with platinum, in the ores of the latter.

Palladium

Palladium is the chemical element with atomic number 46 and its symbol is Pd. It is a rare, silvery-white metal of the platinum group, which it also chemically resembles: it is extracted mainly from some copper and nickel ores. Its most common uses are in industry, as a catalyst, and in jewelry.

Palladium has a white color. It is halfway between platinum and silver. It is somewhat harder than platinum and less ductile. It does not oxidize in air and is the platinum group element with the lowest density and melting point. It is soft and ductile when tempered, considerably increasing its hardness and strength when cold worked. It is used in jewelry for white gold alloys.

Rhenium

Rhenium is the chemical element with atomic number 75 and its symbol is Re. It is a rare, heavy, silvery-white, multipurpose transition metal; chemically it resembles manganese and is used in some alloys. Rhenium is obtained as a by-product of molybdenum refining, and rhenium-molybdenum alloys are superconductors. Rhenium was the last naturally occurring element to be discovered.

Silver

Silver is the chemical element in the periodic table with symbol Ag (from the Latin Argentum) and atomic number 47. It is a soft, white, lustrous transition metal; silver is the best conductor of heat and electricity of all metals, and is found in nature both pure and in mineral form.

Silver is typically worked in 925 millimeters. Silver can be alloyed with all low-melting-point metals, such as zinc (Zn), tin (Sn), and so on. In jewelry, the most common alloy is silver/copper. One of the problems with silver alloys is their darkening, due to the reaction of silver with atmospheric sulfur. The silver-palladium-gold alloy has shown good clinical results in dental uses, with silver being the most abundant metal in these alloys.

In the 1860s, the discovery of silver veins in the American West made this metal superabundant, affecting the economies of nations using a monetary system based on bimetallism.

Indium

Indium is the chemical element with atomic number 49 and its symbol is In. This rare, malleable, low-melting metal is chemically related to aluminum and gallium but even more so to zinc, whose ores are the main source of this element.

Aluminium

Aluminium is now commonplace but was considered to be a precious metal until the late 1800s. Although aluminium is the third most abundant element and the most abundant metal in the Earth's crust, it was at first found to be exceedingly difficult to extract the metal from its various non-metallic ores. The great expense of refining the metal made the small available quantity of pure aluminium more valuable than gold. Bars of aluminium were exhibited at the Exposition Universelle of 1855, and Napoleon III's most important guests were given aluminium cutlery, while those less worthy dined with mere silver. In 1884, the pyramidal capstone of the Washington Monument was cast of 100 ounces of pure aluminium. By that time, aluminium was as expensive as silver. The statue of Anteros atop the Shaftesbury Memorial Fountain (1885–1893) in London's Piccadilly Circus is also of cast aluminium. Over time, however, the price of the metal has dropped. The dawn of commercial electric generation in 1882 and the invention of the Hall–Héroult process in 1886 caused the price of aluminium to drop substantially over a short period of time.

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