Pt850
Pt850
The Japanese 850-fineness platinum standard
Pt850 is a platinum hallmark and fineness standard denoting 850 parts per thousand of pure platinum (85%), with the remaining 15 per cent composed of alloying metals such as palladium, iridium, or ruthenium. The standard is recognised principally under Japanese hallmarking regulations and represents one of three platinum fineness grades commonly stamped on Japanese-market jewellery, alongside Pt900 and Pt950. Pt850 sits at the boundary above which most Western jurisdictions accept the platinum hallmark; the United Kingdom Hallmarking Act, for example, requires a minimum of 850 parts per thousand for the platinum mark.
Properties
The 15 per cent alloying-metal content gives Pt850 noticeably greater hardness than Pt950, with corresponding gains in wear resistance for prong and structural applications. The trade-off is reduced platinum nobility and tarnish resistance and slightly less of the deep platinum-white colour that buyers associate with higher-fineness alloys. Pt850 is workable in the conventional platinum workshop using standard tools and soldering temperatures.
The Japanese platinum market
Japan is the world's largest market for platinum jewellery and has long maintained a hallmarking tradition that recognises Pt850, Pt900, and Pt950 as distinct fineness grades. Japanese consumers typically associate Pt950 with the highest end of fine jewellery, Pt900 with the volume mid-market, and Pt850 with more accessible price points. All three grades are stamped on the inside of the shank or on a discreet location on the piece per Japanese hallmarking convention.
In the trade
Pt850 jewellery is largely a Japanese-domestic phenomenon and is uncommon in Western markets, where Pt950 dominates and Pt900 is the typical secondary grade. Buyers acquiring platinum jewellery in Japan should expect the Pt850 mark on lower-priced pieces and should not assume that any platinum-described jewellery meets the Pt950 standard without checking the hallmark. For exporters and buyers operating across markets, the convention is to specify the fineness explicitly on invoices and to ensure that the hallmark stamped on the piece matches the description used in marketing.