Platinum is a recent addition to the hierarchy of precious metals, having been rediscovered circa the 17th century. Today, platinum is not only prominent in the jewelry and automotive industries, but can also be found in essential platinum-based medicines used for the treatment of certain cancers!
The Prestige of Platinum
The First Platinum and its Rediscovery
Platinum had previously been used in small quantities by civilizations in pre-Columbian South America. The ancient methods used to work platinum were lost. These ancient methods are speculated today to have involved using gold dust to sinter platinum together.
The Spanish rediscovered platinum circa the 17th century when their silver miners encountered a strange new metal. The Spanish named this new metal “platina” (little silver) because they considered it a worthless contaminant. Due to its high miscibility with gold, there were concerns that platina could be used to make counterfeit gold bars or coins. Although these frauds could easily be uncovered through specific gravity calculations, not everyone had the means to do so. Historical reports from the 1750s validate these concerns as counterfeit gold bars originating from The New World were discovered, containing only approximately 10% gold with the rest being “worthless platina.”
Platinum’s Meteoric Rise
Platinum’s rapid rise from worthless contaminate to precious metal is astounding. One hundred years after the first known written reference to platinum in 1748, platinum went from being discarded from silver mines to a precious metal used in a platinum chalice presented to Pope Pius VI, and a platinum medal presented to Napoleon Bonaparte. In 1889 platinum was used to create the International Prototype Kilogram, the object which serves to this date as the definition for the magnitude of a kilogram for the metric system.
In the 20th century platinum’s prestige reached new heights when a platinum crown was made for Queen Elizabeth, the Queen Mother and used in the coronation of King George VI. Later in 1975, platinum became ubiquitous through catalytic converters; today catalytic converters account for approximately 48% of the platinum sold annually.
Modern Platinum Alloys
In jewelry, platinum provides an elegant and sophisticated look. The primary platinum alloys in jewelry today are the 95/5 Platinum/Ruthenium alloy or the 90/10 Platinum/Iridium alloy. As usual for alloy descriptions, the numbers are percentages of total mass, and not volume; which is more important for platinum due to the differences in density between platinum and the alloy additive metals. Pure platinum is extremely rare in jewelry, since pure platinum is very difficult to work with.
95/5 Platinum/Ruthenium Alloy
The 95/5 Platinum/Ruthenium alloy is harder (more scratch resistant) than gold alloys, and as a result offers greater durability. However this alloy also has the highest melting point of common platinum alloys which does affect usability. Due to its increased hardness relative to other platinum alloys, the 95/5 Platinum/Ruthenium alloy typically only accommodates diamonds in settings as more pressure is placed on stones during the setting process. Some jewelers find this alloy is hard on their tools, as well as difficult to solder or burnish. G&S Metals and Refiners carries 95/5 Platinum/Ruthenium alloy in casting grain and also uses this alloy in our platinum sizing stock, round wire, and platinum sheet.
90/10 Platinum/Iridium Alloy
The 90/10 Platinum/Iridium alloy is a softer (less scratch resistant) and has a lower tensile strength than the 95/5 ruthenium alloy, though its tensile strength and hardness surpass other platinum alloys. The advantage of the 90/10 Platinum/Iridium alloy is that it has a lower melting temperature and higher malleability. Many jewelers find that the 90/10 Platinum/Iridium alloy is the best compromise between hardness and malleability. G&S Metals and Refiners only stocks this alloy in our 90/10 Pt/Ir casting grain but can produce mill products in this alloy upon request. This alloy doesn’t meet the stamping requirements to be marked “Platinum” without further qualification in the United States.
Other Platinum Alloys
Other platinum alloys on the market include 95/5 Platinum/Cobalt which has very high hardness but is also much more difficult to work with relative to 95/5 Platinum/Ruthenium however it can also be stamped “Platinum” with no additional qualifications due to its purity. When the price of platinum soared in 2007 other platinum alloys entered the market, however they didn’t prove as popular as the longstanding platinum alloys.
Marking Platinum Alloys
When marking platinum, it is vital to know your alloy and whether it contains other platinum group metals (iridium, palladium, ruthenium, rhodium, and osmium.) Per the US National Stamping act, it is deceitful to stamp, mark, or describe a piece of jewelry with the word “Platinum” or any abbreviation unless it consists of 950 parts per thousand pure platinum. If the platinum piece is lower than 950 parts per thousand pure platinum but contains more than 850 parts per thousand pure platinum it may be stamped with platinum preceded by a number indicating the parts per thousand pure platinum contained within (for example 900 Pt.) Lastly, if a piece of jewelry consists of 950 parts per thousand of platinum group metals, and over 500 parts per thousand pure platinum, the piece may be marked platinum preceded by a number indicating the parts per thousand pure platinum along with the other platinum group metals similarly preceded by a number indicating their part per thousand composition (for example 500 Pt 350 Ir 100 Os.) For the purposes of abbreviation, the use of the first four letters in the metal name or the two letter chemical element symbol is sufficient for identifying all platinum group metals.