Platinum is stronger than gold, harder, heavier, and more scratch-resistant.
Platinum is more expensive than gold, and it is generally manufactured in a much purer form of the metal than is the case with gold.
If a piece of jewelry is at least 95% pure platinum, then it can be marked “platinum”, or one of the usual abbreviations – PT, pt, PLAT, etc.
If the jewelry is at least 75% pure platinum, and most of the rest of the alloy consists of “platinum group metals”, (i.e. iridium, palladium, ruthenium, or osmium), then the piece can be stamped platinum, but an abbreviation of the other predominant metal must be stamped before the word platinum. For example, 10% iridium jewelry would have to be marked “Irid.Platinum” or IRID PLAT.
As with gold, if there is a quality stamp on platinum jewelry, there has to be a trademark right next to it. Look for the quality stamp and the manufacturer’s trademark.