A more thorough explanation:

Assayer

An assayer is a person who tests and analyzes precious metals to determine their purity and value.

• A gold mining company hires an assayer to test the quality of the gold they have extracted from the ground.
• A jeweler may consult with an assayer to verify the purity of the gold or silver used in their jewelry.

These examples illustrate how an assayer is responsible for determining the quality and value of precious metals. They use various methods and tools to analyze the metal and provide accurate information to their clients.