Gold Purity Testing: Karat Meter, Touchstone and XRF

Purity testing is a daily job in any jewellery business, and each method has a place.

Touchstone

Old, cheap, and surprisingly accurate in trained hands. Destructive to a tiny degree and slow.

Karat meter / XRF

Non-destructive and fast. Reads surface composition, so plating can mislead it.

Fire assay

The reference method. Destructive and slow, used where certainty matters.

For staff

Know which method your shop uses and what its blind spot is. That is what a customer dispute turns on.