Precious Metals: Platinum Jewelry
900 & 950 Platinum Jewellery
Source: Australia, Canada, Mexico, Peru, United States
Platinum is a chemical element in the periodic table that has the symbol (Pt) and an atomic number 78. Platinum is a heavy, malleable, precious, grey/white metal that is highly resistant to corrosion, and occurs in some nickel and copper ores. Platinum's wear-resistance, hardness and tarnish-resistance make it well suited for fine jewelry.
Naturally occurring platinum and platinum-rich alloys were first used by ancient Egyptians as well as pre-Columbian Native Americans. Platinum was first identified as an element by European astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia (1713-1773), both appointed by King Philip V to join a geographical expedition to Peru that lasted from 1735 to 1745. Spanish silver miners first named the metal "platina" or "little silver" when they first encountered it in Colombia, South America. The Spaniards dismissed platinum as an 'undesirable impurity' in their mined silver, and often discarded it as a worthless by-product.
Palladium & diamond ring by Niki Kavakonis |
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Platinum is actually an extremely rare metal, occurring as only 5 parts-per-billion (ppb) within the Earth's crust. Today, Platinum is considered more precious than gold. The price of platinum typically costs slightly less than twice the price of pure gold, and platinum being one of the heavier metals, weighs nearly 60 percent more than pure gold. As platinum prices periodically fluctuate, the silvery/white metal palladium has been used as a substitute, due to its similar appearance and durability.
When used in jewelry, platinum is commonly alloyed (900 or 950 platinum) with cobalt, iridium, or ruthenium for increased hardness. For a jewelry piece to be labeled as "platinum" or "PLAT" it must have a "fineness" (millesimal fineness) of at least 95% pure platinum. If the fineness falls below the 95% mark, it must be labeled " IRIDPLAT" which would indicated a platinum alloy with at least 10% Iridium. Platinum is graded as: 850 sterling, 900 sterling, 950 sterling, and 999, which is identified and stamped using the precious metals hallmarking system.
Pure platinum is a softer metal which has a hardness of 3.5 on the Mohs scale, and a Vickers hardness of 110. When alloyed, the Vickers hardness of platinum increases to 130. 900 Iridium/platinum alloy has a melting point of around 1800 C, while other alloys of platinum melt at between 1680 C and 1800 C.
Physical Properties of Platinum
| Name, (Atomic Symbol), # |
platinum, (Pt), 78 |
| Element Category |
transition metals (Group 10, Period 6, Block d) |
| Crystal Structure |
cubic face centered |
| Specific gravity (SG) |
21.45 |
| Mohs Hardness Scale |
4.0 to 4.5 |
| Vickers Hardness (VHN or HV) |
549 MPa |
| Brinell Hardness |
392 MPa |
| Melting Point |
3214.9F (1768.3C, 2041.4K) |
| Boiling Point |
6917F (3825C, 4098K) |
| Chemical Composition |
(Pt) |
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