Start with the complete mark and the piece’s construction. For an uncertain alloy or a valuable item, ask an assay office or qualified jeweller to confirm gold content before you enter a purity.
1. Record the item before testing
Photograph the whole item and any tiny marks under good light. Note colour changes, exposed base metal, solder joints and separate components. Check whether the mark describes solid alloy, gold filling or plating.
2. Treat home observations as clues
Appearance and a magnet do not produce a gold percentage. Many base metals are also non-magnetic. A density result depends on an accurate mass and displaced volume; hollow spaces, stones and mixed construction make it unsuitable for assigning karat to jewellery.
3. Ask what the professional test measures
X-ray fluorescence (XRF) measures elemental composition in the tested area. Ask how the tester checks coatings, solder and different parts. Fire assay is an established laboratory method for gold and requires a sample. Agree on any sampling or damage before handing over an item.
4. Calculate with the reported assay
If the report gives fineness, enter that number directly. Weigh only the confirmed gold-alloy portion. Keep pieces of different purity as separate items in your mixed lot.