Why platinum feels wrong in the hand
Platinum is dense — around 21.4 grams per cubic centimetre, against 19.3 for pure gold and 10.5 for silver. A platinum ring is roughly 40% heavier than an 18K gold ring of identical size, and that heft is the quickest informal check there is. If a white ring feels substantially heavier than it looks, platinum is likely; if it feels light, it is more probably white gold or palladium.
Most platinum jewellery is 950, stamped PT950 or simply PLAT, which by convention means at least 95% pure. Older US and Japanese settings are often PT900. Palladium is the lighter cousin at about 12 grams per cubic centimetre — it looks almost identical to platinum and weighs roughly half as much, and it was widely used for white wedding bands through the 2000s.
Selling it is harder than selling gold
Fewer buyers handle platinum, and the ones who do often quote a wider spread. Refining platinum group metals is a different process from refining gold, so a shop set up to buy gold chain may simply not want it, or may price it cautiously because they will have to send it elsewhere. Expect to make more calls, and expect the percentage of melt on offer to be lower than you would get for the same value in gold.
Palladium has an additional quirk: its price has been far more volatile than gold or platinum, driven mainly by demand from catalytic converters rather than by jewellery. A quote from three months ago may bear no relation to today.