Precious metals
Metals (from the Greek "mine") are chemical elements. Metals are generally divided into precious metals and base metals.
Precious metals do not form chemical compounds with oxygen.
Gold
Latin Aurum, Symbol AU, Density 19.3, Melting point 1063°C
Chemically pure gold is called fine gold. Fine gold is a very malleable metal. For example, it can be beaten into a thin sheet of 0.00011 mm, or wire can be made from 1 g of about 2000 m.
Gold alloys
Gold is only worked in an alloyed state. The main alloying metals used are silver and copper. The addition of silver makes the gold colour lighter, while copper makes it darker. Accordingly, a red gold alloy contains a lot of copper, yellow gold contains about equal parts of silver and copper, and pale gold contains a lot of silver. In white gold, either palladium or iridium is added.
Fineness of alloys
The fineness of precious metal alloys is regulated by the Stamp Act. The fineness is always expressed in 1000 parts. So in the case of a 750/000 gold alloy, of the total 1000 parts of the alloy, 750 parts are gold and the remaining 250 parts are foreign metals.
The commercial gold alloys are
900/000 gold = 900 parts by weight of fine gold + 100 parts by weight of other metals.
750/000 gold = 750 parts by weight of fine gold + 250 parts by weight of other metals
585/000 gold = 585 parts by weight of fine gold + 415 parts by weight of other metals
333/000 gold = 333 parts by weight of fine gold + 667 parts by weight of base metal
Silver
Latin name Argentum, chemical symbol Ag Density: 10.5 Melting point: 960°C
Silver is the brightest white metal and the best conductor of heat and electricity. It is harder than copper and softer than gold. Silver foil can be produced up to 0.002mm thick.
Silver does not oxidise but forms a compound with sulphur. Tarnishing is caused by the formation of silver sulphide on the surface of the metal.
Silver alloys
Silver is usually used in an alloyed state. The metal added is mainly copper.
The most commonly used silver alloy is 925/000, also known as sterling silver.
Platinum
Spanish platina, symbol Pt, specific gravity 21.45, melting point 1774°C.
Platinum has a greyish-white colour with a bluish tinge. It is easy to polish and extremely ductile.
Like the other precious metals, platinum is not worked in its pure state. Commercial alloys with iridium, palladium and copper are common and have a very high fineness (from 800 upwards).
Platinum by-metal:
Rhodium
Chemical symbol: Rh, density: 12.42, melting point: 1966°C
Because of its white colour and its inability to form chemical compounds, rhodium is mainly used in electroplating (e.g. rhodium plating of silver to prevent tarnishing).
Palladium
Chemical formula: Pd, density: 12.03, melting point: 1557 °C
Palladium has a silvery white colour. It plays a special role among the platinum by-metals because it is increasingly used as a jewellery metal. It is also often added as an alloying element to gold (white gold) and platinum.
Iridium
Chemical symbol. Ir, specific gravity 22.65, melting point 2454 °C
Silvery white, brittle and hard, iridium is difficult to form mechanically and is therefore used mainly as a hardness-enhancing alloying metal, especially in platinum alloys.
The platinum by-metals osmium and ruthenium play no role in the precious metals sector.
Precious metals do not form chemical compounds with oxygen.
Gold
Latin Aurum, Symbol AU, Density 19.3, Melting point 1063°C
Chemically pure gold is called fine gold. Fine gold is a very malleable metal. For example, it can be beaten into a thin sheet of 0.00011 mm, or wire can be made from 1 g of about 2000 m.
Gold alloys
Gold is only worked in an alloyed state. The main alloying metals used are silver and copper. The addition of silver makes the gold colour lighter, while copper makes it darker. Accordingly, a red gold alloy contains a lot of copper, yellow gold contains about equal parts of silver and copper, and pale gold contains a lot of silver. In white gold, either palladium or iridium is added.
Fineness of alloys
The fineness of precious metal alloys is regulated by the Stamp Act. The fineness is always expressed in 1000 parts. So in the case of a 750/000 gold alloy, of the total 1000 parts of the alloy, 750 parts are gold and the remaining 250 parts are foreign metals.
The commercial gold alloys are
900/000 gold = 900 parts by weight of fine gold + 100 parts by weight of other metals.
750/000 gold = 750 parts by weight of fine gold + 250 parts by weight of other metals
585/000 gold = 585 parts by weight of fine gold + 415 parts by weight of other metals
333/000 gold = 333 parts by weight of fine gold + 667 parts by weight of base metal
Silver
Latin name Argentum, chemical symbol Ag Density: 10.5 Melting point: 960°C
Silver is the brightest white metal and the best conductor of heat and electricity. It is harder than copper and softer than gold. Silver foil can be produced up to 0.002mm thick.
Silver does not oxidise but forms a compound with sulphur. Tarnishing is caused by the formation of silver sulphide on the surface of the metal.
Silver alloys
Silver is usually used in an alloyed state. The metal added is mainly copper.
The most commonly used silver alloy is 925/000, also known as sterling silver.
Platinum
Spanish platina, symbol Pt, specific gravity 21.45, melting point 1774°C.
Platinum has a greyish-white colour with a bluish tinge. It is easy to polish and extremely ductile.
Like the other precious metals, platinum is not worked in its pure state. Commercial alloys with iridium, palladium and copper are common and have a very high fineness (from 800 upwards).
Platinum by-metal:
Rhodium
Chemical symbol: Rh, density: 12.42, melting point: 1966°C
Because of its white colour and its inability to form chemical compounds, rhodium is mainly used in electroplating (e.g. rhodium plating of silver to prevent tarnishing).
Palladium
Chemical formula: Pd, density: 12.03, melting point: 1557 °C
Palladium has a silvery white colour. It plays a special role among the platinum by-metals because it is increasingly used as a jewellery metal. It is also often added as an alloying element to gold (white gold) and platinum.
Iridium
Chemical symbol. Ir, specific gravity 22.65, melting point 2454 °C
Silvery white, brittle and hard, iridium is difficult to form mechanically and is therefore used mainly as a hardness-enhancing alloying metal, especially in platinum alloys.
The platinum by-metals osmium and ruthenium play no role in the precious metals sector.