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Tuesday 17th October 2017

Platinum Facts

Platinum is a dense (heavy) hard silvery metallic element.
Atomic Number: 78
Atomic Weight: 195.08
Density or Specific Gravity: 21.45
Melting Point: 1768.90 Celsius
Hardness (Moh) 4.3

Platinum Signet Ring

Historical Use
Platinum was used by the South American Indians before the fifteenth century. They could not melt it, but developed a technique for sintering it with gold on charcoal, to produce artefacts. A pre-Columbian platinum ingot was found which contained 85% pure platinum. When the Spanish conquered South America, they discovered the Indians use of platinum, and called it "platina", a diminutive which means "little silver", a somewhat derogatory term. It was considered by the Spanish as a worthless nuisance and impurity.

Platinum Group Metals
Platinum is closely related to five other metals, palladium, ruthenium, rhodium, osmium, and iridium. Together these six are known as the platinum group metals, often referred to as PGMs. They all have somewhat similar atomic structures, leading to some similarity in chemical and mechanical properties, although there are, of course, many important differences.

Processing
In about 1780, Janety was able to refine it using aqua regia, Smith & Tennant developed an arsenic refining method after 1800, the arsenic was used to aid in the melting. This was highly toxic and dangerous, and it is not used nowadays. Until about 1800, it was not realised that there were in fact six different metals. Palladium was not separated and identified until 1803. Platinum's melting point is very high, and consquently it is difficult to melt. It was first melted by Lavoisier shortly after 1800.

Platinum Deposits
Until large deposits were discovered by Merensky at Rustenberg in South Africa in 1924, 93% of the world's supply of platinum came from the USSR. The Rustenberg deposits are considered very rich in platinum. The ratio of platinum to palladium recovered is 2.5%! Currently South Africa supplies around 70%, and Russia about 20% to 25% of the world's production.

1 ounce platinum bar

Platinum in Jewellery
Platinum started to be used in jewellery in Europe about the mid nineteenth century, but it was not until the 1924 find that it started to become commonly used. It became very fashionable during the art deco movement. It possesses very good mechanical properties for jewellery, being strong, and highly durable. It is ideal for stone settings as it has a low "spring-back" rate. In jewellery, like other precious metals it is mixed with other metals to form alloys. Before 1975 there was no requirement for platinum to be assayed and hallmarked in Britain, therefore there was no recognised standard. Because of this, most early pieces marked "plat" or platinum, may be of very variable, and quite low fineness, and most would fail modern assay standards.

This also applies to many pieces marked "18ct & plat". Platinum has been hallmarkable in Britain since January 1st 1975. From then until January 1st 1999, the only officially recognised standard of purity or "fineness" in Britain was 950 parts per 1000. From this year, there are now four standards, which are:-
850
900
950
999
parts per thousand.

Typically platinum is alloyed with copper, iridium, palladium, cobalt, ruthenium, tungsten, gallium or indium. It can also be alloyed with rhodium, osmium or titanium but these are rarely used.

Platinum Diamond Pendant

Purest & Most Precious
Platinum has often been described as the purest, or the most precious metal. Both these claims are slightly inaccurate. The "purest" claim was based on the fact that the highest purity precious metal generally recognised is sterling silver, at 925 parts per thousand (22 carat gold is 916 parts per thousand), but this ignores the fact that Britannia silver, 958 parts per thousand, has been a recognised standard in Britain since 1796.

The price of pure platinum is generally higher than gold, but not always, therefore the claim that platinum is the most precious metal is also a typical marketing exaggeration, besides rhodium is frequently double the price of platinum. As noted previously, the Spanish conquerors of Latin America considered it a worthless nuisance.
Silver has its place in jewellery, particularly for larger and heavier pieces, where its low price means it can be used lavishly. Silver does tarnish very easily, and needs frequent cleaning, which is its major drawback for jewellery. It was used for diamond settings in Victorian gold jewellery, but has been superseded. Again its rapid tarnishing, means it is less than ideal; it is also quite soft, and not durable enough for diamond settings in general.

Certainly now that platinum has earned its recognition as a precious metal, silver is by comparison a poor relation.
For its combination of preciousness and purity, there is no doubt that platinum deserves pride of place, so when we query the claim about platinum being the purest and most precious metal, we are trying to give an accurate honest appraisal on a completely objective basis.

Why is Platinum Expensive
Supply and demand is part of the answer. In recent years, many new industrial uses for platinum have emerged and grown. It is well known as a catalyst in many chemical reactions, and is used in catalytic convertors for car vehicle exhast systems. Because of the high melting point, and the other difficulties in extraction and refining, platinum is expensive to buy and process. This includes higher labour costs for manufacturing it, and also higher expense in recycling it. We can supply any of our own designs in platinum on request.

Platinum Firsts
Platinum was first used for coins in Russia in 1828.
In 1865 some Spanish gold coins were counterfeited using gold plated platinum! Now the platinum fakes would be worth far more than gold originals.
In 1907 Louis Cartier made the first platinum watch.
In 1975, hallmarking of platinum in the UK was started.

Platinum Coins

A Common Error
By the way, we frequently hear people, usually ones who think they know what they are talking about, calling it "Platignum", which is a brand name of pen.