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 (Mohs scale) 4.3
Platinum is closely related to five other metals; palladium, ruthenium, rhodium, osmium, and iridium. Together these six are known as the platinum group metals. They all have somewhat similar chemical and mechanical properties.
Platinum possesses very good mechanical properties for jewelry. It is strong, and highly durable. It is ideal for setting colorless diamonds - there is no color transfer from metal to the stone. Purity of a virgin
In jewelry, platinum is mixed with other metals to form an ALLOY. Typically platinum is alloyed with ruthenium, iridium, palladium, rhodium, copper, osmium or titanium. Platinum has often been described as the purest, or the most precious metal. This is because standard platinum alloy contains 95% of pure platinum as opposed to 75% pure gold in an 18 KARAT gold alloy. The price of pure platinum is generally higher than gold, but not always.
King of Metals; Metal of Kings
Working with platinum is the most pleasant experience for a bench jeweler. All metal we use in our shop starts in the form of grain, rolled stock, wire, or plate.
Using white gold instead of platinum in custom work will not make it less expensive.
It’s easier to make a custom piece using platinum and the result is much more rewarding. The cost of metal in handmade jewelry is relatively insignificant in comparison to the labor.
In comparison to regular yellow gold it is somewhat white, but next to platinum and you will see a distinct yellowish tint in white gold. To hide it virtually all white gold jewelry and watches are rhodium plated. Rhodium is a white metal resembling chromium in color. Coating the surface with rhodium creates an artificially white and faux look which is so common with cheap jewelry and water faucets alike. After a while, plating wears off and the piece looks even worse than in the beginning.
Despite its slightly lower price and lower density resulting in less weight, white gold is not suitable for custom work. It’s harder to work with due to its lower melting point, softness, oxidation, burning, marmiting and porousness of solder.
Platinum
It is alloyed with 5% Ruthenium for hardness and strength. Platinum is commonly alloyed with iridium, ruthenium, cobalt or copper. A platinum content of 950 parts per thousand is required in the US and many other developed countries in order to mark jewelry "Platinum."
An alloy such as platinum/ruthenium is preferred for custom fabrication because of its exceptional properties. However, it is very difficult to cast because of its poor fluidity. Anybody using platinum alloyed with iridium is either not skilled in fine jewelry or using a lot of casting in his/her work. (10% iridium alloy is a warning sign of poor craftsmanship or mass production.)
History
Although platinum was used by the South American natives before the 15th century they could not melt it. Instead they developed a technique for sintering it with gold on charcoal to produce artifacts. A pre-Columbian platinum ingot was found which contained 85% pure platinum.
When the Spanish conquered South America they discovered the natives' use of platinum and called it "platina" a diminutive which means "little silver." It was considered by the Spanish as a worthless nuisance and impurity.
Around 1780 it was refined using aqua regia. Smith & Tennant developed an arsenic refining method after 1800. This was highly toxic and dangerous. Until about 1800 people didn't realize that there were in fact six different metals. Palladium was not separated and identified until 1803.
Platinum's melting point is very high, and consequently it is difficult to melt. It was first melted by Lavoisier shortly after 1800.
Until large deposits were discovered by Merensky at Rustenberg in South Africa in 1924, 93% of the world's supply of platinum came from Russia. Rustenberg deposits are considered very rich in platinum. The ratio between platinum and palladium recovered is 2.5%.
The use of platinum in jewelry in Europe was first reported at the court of Louis XVI of France, around the year 1780. Widespread use of platinum jewelry dates from the late 19th to the early 20th centuries. It was particularly popular in the Edwardian Period jewelry (1901-1914).
It became very fashionable during the ART DECO movement and from this period, platinum became the metal of choice for the finest jewelry up until World War II, when it was requisitioned for military use, and replaced by white gold alloys.
Platinum was first used for coins in Russia in 1828. In the 18th century, Spaniards were counterfeiting Spanish gold coins using gold plated platinum. In 1907 Louis Cartier made the first platinum watch.
Today more than 60% of the world's platinum consumption goes into various industries and science. Its high degree of electrical, thermo electrical and mechanical stability, and high level of resistance to heat and corrosion, have made it irreplaceable in various uses in electronics, precision engineering, the motor industry and radio and television manufacture. Platinum is also widely used in medicine, in the manufacture of surgical instruments.
18K White Gold
The color of a gold alloy depends on the balance of metals with which gold is mixed. Red shades are achieved by increasing the copper content at the expense of silver; pale yellow and green shades are achieved by increasing the silver content at the expense of copper. Copper-rich alloys are harder than silver-rich alloys of the same gold content. White gold was created as a platinum substitute when use of platinum in jewelry was restricted during the war. Platinum was considered a strategic material for military use.
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