BS ISO 24018-2020 Jewellery and precious metals一 Specifications for 1 kilogram gold bar.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 11426. jewellery — Determination of gold in gold jewellery alloys — Cupellation method (fire assay)
ISO 15093. jewellcry and precious metals — Determination of high purity gold, platinum and palladium — Difference method using ICP-OES
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1 cast bar
homogeneous bar produced in a mold directly from melted metal, without further metallurgical treatment after solidification, with a rectangular parallelepiped shape
Note 1 to entry: Usually the cast bar is formed as a truncated pyramid to allow an easier extraction from the mold.
3.2 top surface
one of the two largest surfaces of the bar, which is the last part of the bar to solidify
The minimum fineness of gold bars is 995 %o. The following finenesses are acceptable:
Fineness shall be determined by an appropriate analytical method, including, but not limited to, cupellation in accordance with ISO 11426 for fineness up to 999,5 %o and difference method using ICPOES in accordance with ISO 15093).
999,9 %o fineness shall be determined with 6 significant numbers and with 5 significant numbers for other finenesses, with no rounding up allowed.
IXAMPLE 998,99 %o is marked as 995 %o, 999,896 96o is marked as 999,5 %a (or lower).
4.2 Chemical composition
For a fineness of 999,9 %o, two specifications are available depending on the impurity levels, see Table 1.BS ISO 24018 pdf download.