Overview
ISO 24018:2020 specifies internationally harmonized requirements for cast 1 kilogram gold bars (kilobars) used in investment and industrial markets (jewellery, electronic). The standard covers composition, purity, physical dimensions, surface quality, marking, security features, packaging, transport/storage and the required certificate of analysis - providing a single, practical reference for manufacturers, refiners, assayers, traders and logistics providers dealing with gold bullion.
Key topics and technical requirements
- Purity / title: Acceptable titres are 995 ‰, 999 ‰, 999.5 ‰ and 999.9 ‰. Determination methods include cupellation (ISO 11426) and the difference method using ICP-OES (ISO 15093). Measurement precision rules: 999.9 ‰ needs six significant digits; other titres five; no upward rounding allowed.
- Chemical composition (999.9 specification): Limits for several impurities are specified (examples: Ag ≤ 50 mg/kg, Pd ≤ 50 mg/kg, As ≤ 30 mg/kg, Pb ≤ 10 mg/kg, Si ≤ 50 mg/kg, etc.). All present elements are to be quantified when determining title.
- Physical specification: Mass ≥ 1.00000 kg and ≤ 1.00010 kg (no negative tolerance); dimensions: length 100–120 mm, width 47–56 mm, thickness 7–13 mm.
- Surface quality: Surfaces should be flat and smooth; slight shrinkage on the top surface allowed; no significant cavities, porosity or striations; edges must be safe for handling.
- Marking: Mandatory marks on the top surface only (by stamping, dot-matrix or laser): manufacturer name/logo, metal designation (“Gold” or “Au”), mass (kg/g), title (‰ or %), unique serial number. Optional marks: fineness hallmark, year, “ISO 24018” reference (when applicable), country of origin.
- Security features: Permitted on a side face; if a security feature alters mass it must be disclosed on the certificate of analysis and must not breach physical specs.
- Certificate & packaging: Each bar requires a certificate with mass, titre, serial number, date, manufacturer and signature. Recommended packaging is 25 bars per crate to avoid damage or contamination in transport/storage.
Applications and users
- Bullion refiners and mints producing 1 kg gold bars
- Assay laboratories and quality control teams validating purity and composition
- Jewellery and electronics manufacturers sourcing high-purity gold
- Precious metals traders, exchanges and institutional investors seeking consistent gold bar specifications
- Logistics, storage and insurance providers managing movement and custody of gold bullion
Related standards
- ISO 11426 - cupellation method for gold assay
- ISO 15093 - high-purity Au/Pt/Pd determination by ICP-OES difference method
Keywords: ISO 24018:2020, 1 kilogram gold bar, gold bar specifications, gold purity, precious metals standard, gold bullion, certificate of analysis.
