Platinum is a dense, precious, silverish-white transition metal that is naturally occurring. It is characterized by remarkable chemical inertness and an extremely high melting point of about 1,768 degrees Celsius. These properties make it highly resistant to corrosion and tarnishing, which is why it is classified as a noble metal. Its rarity in the Earth’s crust, occurring at an average abundance of only about five micrograms per kilogram, contributes significantly to its high value.
Natural Occurrence and Forms
Platinum is found in the Earth’s crust in two primary forms, each representing a different geological history. It can occur as native platinum, often as small grains or nuggets in alluvial or placer deposits. This native form is rarely pure and is typically alloyed with other Platinum Group Elements (PGEs) such as iridium, palladium, and osmium, as well as with iron.
Instead of native deposits, platinum is primarily recovered from specific ore minerals, most commonly disseminated within sulfide ores of copper and nickel. Key platinum-bearing minerals include sperrylite (a platinum arsenide) and cooperite (a platinum sulfide). These ore minerals represent the largest resource for platinum production today.
Key Global Sources and Deposits
The world’s supply of platinum is heavily concentrated in a few geologically unique locations. The single most important source is the Bushveld Igneous Complex in South Africa, a massive, saucer-shaped layered intrusion of igneous rock. This complex contains the world’s largest known reserves of Platinum Group Metals and accounts for the vast majority of global annual production. Within the Bushveld Complex, the metal is mined from distinct, mineral-rich layers known as reefs, such as the Merensky Reef and the UG2 Reef.
Other significant, though smaller, deposits are found in Russia, particularly in the Norilsk-Talnakh region of Siberia. There, platinum is often extracted as a byproduct of large-scale nickel and copper mining operations. North America also contributes to the supply, with deposits such as the Stillwater Complex in Montana and the Sudbury Basin in Canada.
The Process of Extraction and Refining
Extracting usable platinum from its ore is a laborious and energy-intensive multi-stage process. The initial steps involve deep underground mining, where the ore is crushed and milled into a fine powder. This powder then undergoes a process called froth flotation, which uses air bubbles and chemical reagents to separate the platinum-bearing minerals from the bulk of the waste rock.
The resulting concentrate is subjected to high-temperature smelting, often exceeding 1,500 degrees Celsius, which removes many impurities and creates a matte rich in base metals and PGEs. This matte is then sent for chemical refining, where the individual Platinum Group Elements are separated. Techniques involving chemical dissolution, such as using a mixture of hydrochloric and nitric acids called aqua regia, are employed to isolate the platinum. This entire journey, from mining the ore to achieving a pure platinum product, can take up to six months, with several tons of ore required to yield a single ounce of the finished metal.