K24 is the Japanese marking convention for 24-carat or pure gold, indicating an alloy of 1,000 parts gold per 1,000, equivalent to fine gold and to the term Junkin. In commercial practice K24 is used to indicate gold of nominal one thousand fineness, with the actual fineness depending on the producer's standard, typically 999.0 or higher for retail items and 999.9 for investment-grade ingots.

Marking convention

The K24 mark follows the same self-applied Japanese carat-marking convention as K18 and K22. K24 is the highest carat designation used in the marking system and is reserved for fine gold. Items marked K24 are by definition pure gold, although in international trade-association practice the actual fineness should be specified separately on accompanying documentation, with 9999 fine and 999.0 fine treated as different commercial grades.

Production characteristics

Pure gold is too soft for most jewellery applications, with a Mohs hardness of around 2.5 and very low tensile strength. K24 is therefore used in Japanese practice principally for investment ingots and bars, presentation items including small commemorative leaves and plaques, traditional Buddhist devotional objects, and a limited range of jewellery items where the cultural or symbolic value of pure gold is the point and where structural demands are low. Tea-ceremony objects, incense containers and religious items are sometimes produced in K24.

Use in jewellery

K24 jewellery in the strict sense is uncommon. Where it appears, it is typically in plain bangles, chains, pendants and small ear studs of conservative design, intended for gifting or for cultural occasions rather than daily wear. The high gold content makes the items both materially and culturally distinctive but leaves them vulnerable to deformation and scratching.

Trade significance

K24 marking is the Japanese equivalent of the international 9999 or 999.0 fine gold standards, depending on the producer's specification. The marking is a useful identifier in the second-hand and estate trade for Japanese-produced fine-gold items, particularly in markets such as Hawaii where the volume of Japanese tourist purchases over decades has produced a substantial pool of K24-marked items in resale circulation.