In the classification of mineral deposits, the pge deposits belong to the natural platinum subgroup and contain the natural elements of iridium, rhodium, palladium and platinum. They widely exist in the phenomenon of isomorphism replacement between each other, and then form a series of isomorphism mixed crystals. The metals smelted by platinum group elements include palladium, rhodium, iridium, platinum and so on.

Platinum and palladium are the two minerals with the smallest deposits in the platinum group. Due to their similar metallurgical properties, they are often used as substitutes for each other in various applications.

Platinum group metals include platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), ruthenium (Ru) and rhodium (Rh).

Platinum-group metals are well known for their valuable functions and rare resources. Together with gold and silver, it is called "precious metal". However, its discovery and use were much later than gold and silver. Gold and silver ornaments have been found in the tombs before human beings. However, the understanding and use of platinum group metals by human beings only started more than 200 years ago. Platinum was discovered as early as 1735 by A.D.U. lloa, while other elements were not known continuously until the 19th century, such as palladium by w.h.wollaston in 1804 and ruthenium by k.laus in 1845. Although they were discovered relatively late, it was soon realized that they have some valuable functions and are thus widely used in modern industry and cutting-edge technology. Hence it is called "modern precious metal". It is reported that from 4000 BC to the end of the 19th century, a total of 29,000 tons of gold were produced in the world. From 1973 to 1980, the international average annual output reached 1375t. The international output value of platinum group metals exceeded 100t from 1969, doubled in the late 1980s, and reached 200t (zhang wenpu, 1997), with an annual output of nearly 300t in the early 1990s. From these data, it is not difficult to understand the deep meaning of "precious metal" and "modern precious metal" : both of them are rare and precious, while the number of platinum group elements is certainly not as large as gold and silver, but the speed of its development deeply reflects the meaning of "modern".

Platinum group metals have similar physical and chemical properties as well as their own characteristics. Together they have the following characteristics: all are silver white except for osmium and ruthenium, which are steel grey; High melting point, high strength, stable electric heating, high resistance to electric spark corrosion, excellent corrosion resistance, high temperature oxidation resistance, excellent catalytic activity. Their respective characteristics determine their different USES. For example, platinum has excellent plasticity and stable resistance and resistance temperature coefficient, which can be forged to form platinum wire and platinum foil. It is not directly combined with oxygen, not acid, alkali corrosion, only dissolved in hot; Palladium is soluble in concentrated nitric acid and can absorb 350 ~ 850 times its volume at room temperature. Rhodium and iridium are insoluble and react with fusion to form compounds soluble in acids. Osmium and ruthenium are insoluble but readily oxidize into tetroxide.

More than 200 kinds of platinum group elements have been discovered. Can be divided into four categories: (1) natural metals: natural platinum, natural palladium, natural rhodium, natural osmium and so on; (2) metal intermetallides: palladium platinum ore, osmiridium ore, ruthenium-osmiridium iridium ore, and platinum group metal and iron, nickel, copper, gold, silver, lead, tin and other metal bond combination of metal intermetallides; (3) semi-metallic intermetallides: platinum, palladium, iridium, osmium and other bismuth, tellurium, selenium, antimony and other with metal bond or with appropriate metal bond components of covalent bond compounds; (4) sulfide and arsenide. Primary mineral deposits of pge and their composition are shown in table 3.17.2. The main industrial mineral deposits are arsenic platinum ore, natural platinum, bismuth telluride palladium ore, bismuth telluride palladium ore, arsenic platinum osmium ore, palladium telluride iridium ore and bismuth telluride palladium nickel ore. Arsenoplatinite and equiaxed bismuth telluride palladium are common in primary platinum deposits, and natural platinum is mostly produced in paliumite. & have spent Rare metals are the general term for precious and rare metals. Because e gold and silver by the people's bank of China franchise, the material part of the operation of the precious metal is the first platinum group elements, and selenium, tellurium, arsenic are rare elements, commonly known as semi-metal.

Platinum: platinum is a silver-white metal with a melting point of 1769 degrees and a density of 21.45g/cm3. It is mainly used for electrical appearance, chemical industry and manufacturing of fine alloys.

Palladium: palladium is silver gray metal, melting point of 1552 degrees, density of 12.16g/cm3, good plasticity, poor corrosion resistance in precious metals, power supply, appearance, chemical industry and manufacturing fine alloys.

Rhodium: rhodium is a smoky grey metal with a melting point of 1960 degrees and a density of 12.44g/cm3. It is a brittle metal. Power supply gas, appearance, high temperature alloy and fine alloy, etc.

Iridium: iridium is a silver-gray metal with a melting point of 2,443 degrees, the highest of any precious metal. With a density of 22.4g/cm3, it is a brittle metal with stable chemical properties, acid and alkali corrosion resistance and high hardness. For electrical, chemical, appearance, light industry and other aspects, the manufacture of fine alloys.

Gallium: liquid gallium for silver white metal, solid gallium for blue crystal metal, soft texture, melting point of 29.8 degrees, the density is 5.9g/cm3, in the air chemical function safe, gallium is primarily used in the semiconductor industry, manufacturing thermometers, manufacturing fusible metal.

Indium: indium is a silver-white metal with a melting point of 156.6 degrees and a density of 7.31g/cm3. It is softer than lead, with good ductility and stable chemical function. It is mainly used in the manufacturing of precious metal alloys, low-melting point alloys, bearing alloys, electroplating and other industries.

Selenium: selenium is a black or dark gray glassy amorphous ingot (red selenium and gray selenium are crystalline variants of selenium, the main component remains unchanged), attributed to the scattered elements, also known as semi-metal. Selenium melting point of 220 degrees, boiling point of 685 degrees, density of 40808g/cm3, brittle, mainly used in the manufacture of rectifier, selenium plate, copy drum, alloy, enamel and glass industry.

Tellurium: tellurium is a silver gray semi-metal, is a rare element, melting point of 450 degrees, density of 6.24g/cm3, brittle, has a high resistivity, is a diamagnetic metal, so it is an outstanding semiconductor material. Mainly used to manufacture semiconductor equipment, alloys, chemical raw materials and cast iron, rubber, glass and other products additives.

Arsenic: arsenic is a silver gray semi-metal and a rare element. Arsenic is easily oxidized in the air. Its oxide is highly toxic (commonly known as arsenic). The density of arsenic is 5.73G/cm3.