Metal Guide
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 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. Platinum Facts: Atomic Number: 78; Atomic Weight: 195.08; Density or Specific Gravity: 21.45; Melting Point: 1768.90 Celsius and Hardness (Moh) 4.3.
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 realized 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.
What are the marks inside my platinum jewelry? You're familiar with the gold standard, where 24k = 100%. The platinum standard is based on parts per thousand, where 1000 parts = 100%. All platinum alloys are derived from this standard. The two most common platinum alloys found in the US. 95% Platinum: This alloy is 950 parts per 1000 and 50 parts other metals. Common quality marks are: Platinum, Plat, Pt, Pt950, 950Pt, 950Plat and Plat950. 90% Platinum: This alloy is 900 parts per 1000 and 100 parts other metals. Common quality marks are: 900Pt, Pt900, and 900Plat. 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.
Why is platinum's purity important to me? Two reasons. First, your skin. Platinum is hypoallergenic and resists tarnish, making it easy for sensitive people to wear. Second, platinum's purity makes it one of the strongest, most durable metals in the world. Platinum has often been described as the purest, or the most precious metal. Both these claims are slightly inaccurate. 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.
Gold's natural color is further enhanced by alloying it with small amounts of other metals. Jewelers create yellow, rose, green and white golds by using different alloys. More copper results in a soft rose color; additional silver creates green gold; and palladium produces white.
Gold is very durable and look no further than the nearest museum where gold jewelry, coins and artifacts from ancient civilizations attest to the metal's enduring beauty and permanence. Jewelers throughout the ages have preferred gold to all other metals for its beauty and ease of workmanship. Gold can be melted, or shaped, to create any design. It can be alloyed with a number of other metals to increase its strength and produce a variety of colors.
Colors of Gold: Gold comes in a variety of colors. Because gold is alloyed with other metals to increase its strength, it can also be made in a variety of colors. For example, yellow gold is created by alloying the metal with copper and silver; using copper only creates pink gold; white gold contains platinum or palladium, zinc and copper; green gold contains silver, copper and zinc.
24K Gold: Pure gold, or 24-karat, is generally considered too soft for use in jewelry, so it is alloyed with other metals to increase its strength.
18K Gold: 18K Gold is 18/24ths, or three-quarters pure gold. Jewelry of this fineness is marked "18k" or "750," meaning 75 percent gold.
14K Gold: In the United States, 14-karat gold is used most commonly for jewelry. Fourteen-karat gold is 14/24ths, or slightly more than one-half pure gold. Jewelry of this fineness is marked "14k" or "585," the European designation meaning 58.5 percent gold.
10K Gold: Nothing less than 10-karat gold can be legally marked or sold as gold jewelry in the United States. These pieces are marked "10k" or "417," the European designation meaning 41.7 percent gold.
Stamping: Look for trademarks accompanying the quality mark. When a piece of jewelry is stamped with a quality mark, law requires that it be stamped with a hallmark or trademark as well. Sometimes the jewelry is also marked with its country of origin. These designations are designed to assure you that you are buying genuine gold jewelry of the karatage marked.