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25/06/2024
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Platinum: What’s So Special About the Shiny Metal?

Platinum is coveted for its rarity, resilience and versatility. Its scarcity makes the noble metal exclusive and valuable, while its resistance to corrosion and ability to withstand extreme conditions make it ideal for various industries.

If phrases like “platinum status” and “going platinum” are to be believed, the precious metal is the best and baddest in all the land. But how elite is platinum actually, particularly when compared with its best frenemy, gold?

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Platinum, classified as a chemical element with the symbol Pt and atomic number 78, stands as a rare and lustrous metal.

Its identity as a pure platinum substance, defined by its unique arrangement of platinum atoms, is characterized by exceptional traits: remarkable density, outstanding resistance to corrosion and an exceptionally high melting point. These inherent attributes render platinum indispensable across diverse industries.

Platinum, though relatively scarce, is discovered naturally in tandem with other platinum metals, including palladium and rhodium. Prominent platinum-producing regions encompass South Africa, Russia and Canada but it can also be found in North and South America.

The majority of native platinum is mined in South Africa, particularly in the Bushveld Complex region, which contains one of the world’s largest known platinum reserves. This region accounts for a significant portion of global platinum production.

With historical roots extending to pre-Columbian civilizations in South America, platinum derives its name from the Spanish term “platina,” signifying “little silver.”

Uncovering Platinum

William Hyde Wollaston and Smithson Tennant, both distinguished chemists of the late 18th and early 19th centuries, made notable contributions to the field of chemistry related to platinum and its reactions with certain acids.

Wollaston is renowned for devising a method to dissolve platinum in aqua regia, a potent mixture of nitric and hydrochloric acids. This achievement was significant because platinum is highly resistant to chemical reactions, but aqua regia could dissolve it. This breakthrough enabled further analysis and processing of platinum, eventually leading to the development of malleable platinum.

Tennant, in collaboration with Wollaston, conducted extensive research on platinum group metals, including their interactions with acids.

Their combined efforts involved analyzing various platinum ores and residues led to the identification and characterization of several new elements within the platinum group, such as iridium and osmium. These discoveries were made possible through the reactions of these metals with acids and subsequent chemical analysis.

Platinum vs. Gold

Platinum is a naturally occurring chemical element that is actually about 30 times rarer than gold, according to Jenny Luker, president of Platinum Guild International USA (PGI), a marketing organization for the platinum jewelry industry.

“If all the platinum ever mined were melted and poured into an Olympic-sized pool, the platinum would barely reach your ankles. Gold, however, would fill three pools,” she explains via email. In fact, it’s the least common of all the popular precious metals.

Visual Characteristics

In appearance, platinum metal is silvery-white and shiny. Because it looks so similar to white gold, the distinction can be confusing to the untrained eye.

“White gold is actually yellow gold that was mixed with other metals and then plated with rhodium to appear more white — a white mask that will unveil a yellow tinge over time,” Luker says. “Platinum, on the other hand, will maintain its naturally white color.”

That’s not to say that it won’t change at all, however. “If you look closely at a piece of well-loved platinum jewelry, you’ll notice a satiny finish on the surface that developed over time. This change in texture is known as ‘patina,'” Luker explains. Many platinum aficionados actually desire this change in appearance.

Durability

Platinum is also more durable than gold, which is one of the reasons it is often the metal of choice for engagement rings, (gold prongs are more likely to break than their platinum counterparts.)

Unfortunately, all of these attributes have given platinum a traditionally heftier price tag than gold, although Luker notes that the current price difference is minimal.

“Right now, the price per ounce of platinum is actually lower than gold. However, because platinum jewelry is more pure (typically 95 percent platinum versus 58.5 percent gold in 14 kt. gold jewelry) and more dense than gold, it will still cost a bit more than a similar gold ring,” she notes. (On October 2, 2023, the price of platinum was $894.05 per ounce. Gold was $1,837 per ounce.)

Mining the Precious Metal

Platinum is mined mainly in South Africa but is also sourced in Russia, Zimbabwe, the United States and Canada. Platinum mining involves several common types of mining methods, each suited to different geological conditions and deposit types.

Underground Mining

There are a few types of undergrounding mining methods. In shaft mining, vertical shafts are excavated to access deep ore bodies. Miners use elevators and hoists to transport workers and materials to the underground mine.

In decline or adit mining, horizontal tunnels, known as declines or adits, are driven into the ore body from the side of a hill or mountain, allowing access to underground deposits without the need for a vertical shaft.

And finally, room and pillar mining is a method in which the ore body is divided into chambers or rooms, leaving pillars of ore to support the roof. This method is suitable for deposits with stable rock conditions.

Open-pit Mining

For this type of mining, large, deep pits are excavated to access ore bodies near the surface. This method is used for shallow deposits and can result in significant environmental disturbances due to the excavation of large areas.

Open-pit mining, while effective for shallow platinum deposits, can result in significant environmental disturbances due to the excavation of large areas, making it a less favored method in many mining operations today.

Alluvial Mining

Alluvial mining is the extraction of valuable minerals from sedimentary deposits, typically found in riverbeds, floodplains or areas where water has transported eroded materials.

It begins with natural erosion, where geological forces dislodge minerals from their sources. Water carries these materials, depositing them when its velocity decreases. Miners manually or mechanically extract these sediments, concentrating on valuable minerals like gold, diamonds or platinum.

Techniques such as panning and gravity separation are used to separate valuable minerals from less valuable components. After concentration, further processing, including refining or smelting, occurs to obtain the final product.

This method is often used for easily transportable minerals and varies based on the target mineral and scale of mining.

Heap Leaching

This process is used to extract valuable metals, often from low-grade ores. In this method, the ore is crushed and stacked into heaps or piles. Then, a leaching solution, typically containing chemicals like cyanide, is applied to the ore heap. Over time, the solution percolates through the heap, dissolving the target metals.

The dissolved metals are then collected and further processed to extract the desired metal, while the remaining waste material is typically disposed of in an environmentally responsible manner. Heap leach mining is a cost-effective technique for certain types of ore bodies.

In-situ Recovery (ISR)

In-situ recovery (ISR), also known as in-situ leaching or solution mining, is a mining method used for extracting valuable minerals from ore bodies without physically removing the ore. Instead, a leaching solution is injected directly into the ore deposit underground.

This solution dissolves the target minerals, and the resulting pregnant solution is pumped to the surface for processing. ISR is considered environmentally friendly because it minimizes surface disturbance and waste generation, making it a preferred method for certain types of deposits.

Common Platinum Uses

Although platinum’s strength and beauty have made it a favorite amongst jewelers and consumers, the silver-white metal has an array of uses, some of which are pretty surprising.

Catalysis

Platinum is used as a catalyst to make chemicals like silicone, nitric acid and benzene. In fact, the six platinum group metals (iridium, palladium, platinum, rhodium, ruthenium and osmium) are all known for their impressive catalytic skills (meaning these metals increase the rate of chemical reaction between substances without changing their physical properties.)

Auto Parts

In the automotive industry, platinum is a key component of catalytic converters. In fact, about half of platinum’s demand is actually for use in catalytic converters for transportation vehicles like buses, cars and trucks.

These devices convert harmful exhaust gases, such as carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons, into less harmful substances like carbon dioxide (CO2), nitrogen and water vapor.

Jewelry

Platinum and platinum wire are prized materials in jewelry-making for several reasons. Their natural, silvery-white sheen provides a timeless and elegant appearance that complements various gemstones and designs. Platinum’s exceptional durability ensures that jewelry remains unblemished over time, making it a perfect choice for heirlooms.

Platinum wire — thin, flexible strands made from the precious metal platinum — has a malleability that allows for intricate and delicate craftsmanship. Also, platinum’s hypoallergenic properties make it suitable for those with sensitive skin.

Healthcare

In the healthcare field, platinum compounds are a component of some chemotherapy drugs, and are also used in pacemakers and even dental fillings. The electronics industry has various applications for platinum, too — for instance, computer hard disks.

Cisplatin is a platinum-containing compound used as a chemotherapy drug to treat various types of cancer. It works by interfering with the DNA in cancer cells, preventing their replication and growth. Other platinum-based chemotherapy drugs include carboplatin and oxaliplatin.

Military Applications

From a defense standpoint, platinum has been long valued for its strength, which goes far beyond simple scratch resistance. The metal holds up well under high temperatures, boasts stable electrical properties and is highly resistant to chemical attacks.

For example, coating jet engine blades with platinum-based products protects them where temperatures can reach 2,000 degrees Celsius (3,632 degrees Fahrenheit).

“Platinum was an important strategic defense metal used during World War II and was not allowed for jewelry application at that time,” Luker says. Even today, platinum is so important to economic and defense efforts that it was listed as one of the 35 minerals “deemed critical to U.S. national security and the economy.”

With a resume like that, it appears that platinum’s reputation and price tag are well deserved, indeed.

 

Source: how stuff works

 

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