Glossary

In a hallmarking context, assaying is the scientific testing of gold, silver, or other precious metals using methods like XRF spectrometry or fire assay (cupellation) to determine the exact percentage of pure metal present.

BIS operates under the Ministry of Consumer Affairs, Food & Public Distribution and sets quality standards for gold and silver articles. All hallmarking in India must be done through BIS-authorized centres.

The BIS hallmark consists of a triangular BIS logo, purity/fineness number (e.g. 916 for 22K gold), and a unique six-digit HUID number. It provides consumers with an assurance of purity from an independent testing laboratory.

Fineness is the standard system used in hallmarking to denote purity. For gold: 999 = 24K (pure gold), 916 = 22K, 750 = 18K, 585 = 14K. For silver: 999 = pure silver, 925 = sterling silver. The fineness number is stamped directly on the hallmarked article.

Fire assay involves taking a small sample of the metal, wrapping it with lead foil, and heating it in a cupel (a porous ceramic crucible) at temperatures above 1,000°C. The base metals are absorbed into the cupel, leaving behind a bead of pure precious metal that is then weighed. It is considered the referee method for precious metal analysis.

Introduced by BIS in July 2021, the HUID system replaced the older jeweller's mark. Each piece of hallmarked jewellery receives a unique six-character alphanumeric code that can be verified online via the BIS Care app, enabling end-to-end traceability from assaying centre to consumer.

The karat system divides gold purity into 24 parts. 22K gold means 22 parts gold and 2 parts other metals (91.6% pure gold). Common standards in India include 24K (999), 22K (916), 18K (750), and 14K (585).

While still used for quick preliminary checks, touchstone testing has largely been replaced by XRF spectrometry for official hallmarking purposes due to the latter's superior accuracy and non-destructive nature.

A troy ounce is heavier than a regular (avoirdupois) ounce and is the global standard for trading gold, silver, platinum, and palladium. International bullion prices are quoted per troy ounce.

XRF spectrometry works by irradiating the sample with high-energy X-rays, causing the sample to emit secondary (fluorescent) X-rays characteristic of each element present. It is the primary method used in hallmarking centres for rapid, non-destructive purity testing of gold and silver articles.