Platinum in jewelry is normally a 90-95% alloy. The most commonly used in the United States are:
Pt900/Ir: 90% Platinum, 10% Iridium
Pt950/Ir: 95% Platinum, 5% Iridium
Pt950/Co: 95% Platinum, 5% Cobalt
Pt950/Ru: 95% Platinum, 5% Ruthenium
Out of the three precious metals (gold, silver, and platinum), platinum is the densest and lasts the longest. When platinum jewelry is scratched, it does not lose volume like gold and silver. The wear and tear on platinum jewelry is called Patina and is highly regarded in Japan to honor the history of the item. Patina can be easily buffed out if needed to restore its original luster.
Although originally used more than 2,000 years ago for decorative purposes, only recently has platinum returned in popularity within the jewelry industry, and more specifically, for engagement and bridal rings. As of 2013, it is estimated that China is responsible for more than half of the world's demand for platinum jewerly.
Platinum's market price is highly volatile due to its rare nature (only about 200 tonnes produced each year) and geographic concentration of production (South Africa controls 70% of the world's production). Investing in platinum has a high risk and is increasingly affected by the overall investment industry through speculators and new investment vehicles (exchange traded funds).
Platinum is produced by mining ore and separating it from the other minerals through various refining processes. In some mines, it takes up to 40 tonnes of ore to produce 1 ounce of platinum, accounting for the majority of the price of platinum.
Recently, platinum has been in the news because of labor issues within South Africa's mining companies. Since South Africa controls 70% of the world's supplies, these issues are closely watched in order to determine what affects they will have on the market price of platinum.