Platinum is a precious metal that costs more than gold. It usually is mixed with other similar metals, known as the platinum group metals: iridium, palladium, ruthenium, rhodium and osmium.

Different markings are used on platinum jewelry as compared with gold jewelry, based on the amount of pure platinum in the piece. The quality markings for platinum are based on parts per thousand. For example, the marking 900 Platinum means that 900 out of 1000 are pure platinum, or in other words, the item is 90% platinum and 10% other metals. The abbreviations for platinum – Plat. or Pt. – also can be used in marking jewelry.

Items that contain at least 950 parts per thousand pure platinum can be marked simply platinum. Items that have at least 850 parts per thousand pure platinum can be marked with the amount of pure platinum and the word platinum or an abbreviation (for example, 950 platinum, 900 Plat. or 850 Pt.). Jewelry that contains less than 850 parts per thousand pure platinum, but has a total of 950 parts per thousand of platinum group metals (of which at least 500 parts is pure platinum), may be marked with both the amount of pure platinum and the amount of the other platinum group metals in the piece. For example, the marking 600 Plat. 350 Irid. means that the item has 600 parts per thousand (60%0 platinum, and 350 parts per thousand (35%) iridium, totaling 950 parts per thousand of platinum group metals, and 50 parts per thousand (5%) other metals.