Assays and Certificates of Authenticity

An assay is the analysis used to test the purity and composition of a precious metal. In gold and silver, the assay ensures that coins and bars meet the mint’s stated standards. For example, if a mint claims its coin is 99.9% pure gold, the assay confirms this before the coin is released.

Historically, assaying was common when gold and silver circulated as currency. While that era has passed, assays remain essential for today’s collectors and investors to verify purity, protect value, and maintain trust.

The Assaying Process

Assayers take a sample of the metal—either shavings or molten material—before testing it through one of several methods:

• Dry Assay – Uses fluxes and heat to separate pure metal from impurities.
• Fire Assay – A traditional method that melts metals in a crucible to identify impurities.
• Wet Assay – Dissolves metals in solvents for chemical analysis.
• X-Ray Fluorescence (XRF) – Uses X-ray beams to measure purity based on emitted radiation.
• Spectrograph Assay – Applies electrical discharge to a sample and measures emitted light.
• Other Methods – Titration for silver, cupellation for gold, and plasma spectrometry for platinum.

Each method ensures that the final product meets claimed purity standards.

Why Assays Matter

For investors and collectors, assays provide confidence that gold, silver, platinum, or palladium products are legitimate. They protect buyers from fraud and give sellers proof of purity when liquidating metals.

Types of Assay Documentation

Most precious metals are sold with assay documentation. Common forms include:

• Assay Cards – Typically small cards included with bars or coins, listing purity, weight, serial number, and mint logo.
• Assay Certificates – Formal documents verifying purity and authenticity.

Both offer traceability, authenticity, and assurance of purity.

Certificates of Authenticity (COA)

A certificate of authenticity (COA) is another safeguard. Unlike an assay, it does not test purity. Instead, it verifies origin and authenticity, often with details such as:

• Maker’s mark
• Weight and fineness
• Stamp of approval or seal

COAs are most often included with commemorative coins, special releases, or limited editions. Bars rarely come with them unless issued in unique circumstances.

Precious Metals That Include Assays or COAs

• With Assay Cards – Gold bars, silver bars, platinum bars, palladium bars, and sometimes limited-edition coins.
• With COAs – Special release coins, commemoratives, or other collectible items.

Key Takeaways

• An assay verifies purity and ensures mint claims are accurate.
• A certificate of authenticity confirms legitimacy but does not measure purity.
• Both documents protect investors and collectors when buying or selling precious metals.