Platinum is the most precious metal commonly found in jewelry. It was used by ancient Egyptians in 700 BC as a decoration. The Indians in pre-Columbian South America worked it together with gold to create various items of jewelry. Platinum was the metal of choice in the US from the turn of the century to the 1940's. During World War II, platinum was declared a strategic metal, and its use was banned in all non-military applications. Platinum never regained its popularity after the war until 1992 when the Platinum Guild International, USA was formed to help promote the use of the jewelry. Since it was founded, the sale of platinum has risen 1000%.
Like gold, platinum is rare and heavy, but it is more durable than gold and is sold in purer form. Most platinum is 90 - 95% pure platinum, compared to 18k gold, which is only 75% pure. It is sometimes mixed with a little bit of iridium and ruthenium, which are similar to platinum but much rarer, for added strength.
Platinum is much heavier than gold. 90% pure platinum weighs 60% more than 14k gold. A six inch cube of platinum will weigh 160lbs.
Platinum is very strong. It is one of the strongest and most enduring metals. Its strength holds gemstones very securely in their settings.
Platinum is not sold according to karat weights. It is stamped Pt or PLAT in the United States to indicate that it is platinum.
Because of its purity, platinum is hypoallergenic so it will not cause an allergic reaction like alloys in other metals sometimes do. Its light color also makes it popular. Like white gold, it makes very white diamonds appear bright.