Pt900
Pt900
The Japanese 900-fineness platinum standard
Pt900 is a platinum hallmark and fineness standard denoting 900 parts per thousand of pure platinum (90%), with the remaining 10 per cent composed of alloying metals such as palladium, iridium, ruthenium, or cobalt. The standard is principally associated with Japan, the world's largest market for platinum jewellery, where Pt900 sits between Pt850 and Pt950 in the recognised hallmarking hierarchy. Pt900 also enjoys broader international recognition than Pt850 and is accepted under most national platinum standards as a legitimate platinum grade.
Properties
The 10 per cent alloying-metal content gives Pt900 noticeably greater hardness than Pt950, with corresponding gains in wear resistance for prong and structural applications. The colour and tarnish resistance remain those of platinum: full white, fully noble, fully hypoallergenic. The trade-off is fractionally lower platinum content per unit weight and a small reduction in the deep platinum-white visual character compared to Pt950 finished to the same polish.
The Japanese context
Japan's platinum jewellery market has historically operated on three recognised fineness grades — Pt850, Pt900, and Pt950 — with Pt900 occupying the volume mid-tier. Japanese consumers associate Pt900 with mainstream fine-jewellery quality, with Pt950 reserved for the highest-end pieces. Japanese hallmarking regulations require explicit stamping of the fineness on every platinum article, so buyers in Japan can verify the grade at point of sale.
In the trade
Outside Japan, Pt900 is encountered most often in pieces produced for the Japanese domestic market or imported from Japan, and occasionally in continental European production. In the principal Anglophone fine-jewellery markets — the United States, the United Kingdom, Canada, Australia — Pt950 is the dominant standard and Pt900 is comparatively rare. Buyers acquiring platinum jewellery internationally should confirm the stamped fineness rather than assuming a default grade.