Platinum is a very scarce metal, thirty-five times rarer in nature than gold. The platinum used in jewelry is 95% pure platinum combined with 5% of other metals.
Since platinum is such a hard metal, it will not wear down and jewelry made from it will retain the same shape for a lifetime.
Platinum is heavier than gold and appreciated by those who like the feel of heavier, more substantial jewelry which does not look weighty.
Platinum is naturally white and will not fade or change color. However, platinum jewelry will naturally acquire a patina - a special sheen - from daily wear. Some people prefer the patina look, but others prefer to have their platinum jewelry professionally repolished from time to time.
Platinum, because of its relative scarcity, is significantly more expensive than gold. It is a popular choice for engagement rings.