Hallmarks to look for
Stamps like 10K, 14K, 18K, 750, 585, or 417 indicate purity. Plated or filled pieces may say GP, GF, or HGE — those are not solid gold and have little melt value.
Reference
Karat & purity guide
Karat tells you how much of a piece is pure gold. 24K is essentially pure; 18K is 75% gold; 14K is 58.3%. Lower karat alloys are harder and more common in everyday jewelry.
| Marking | Karat | Purity | Notes |
|---|---|---|---|
| 24K · .999+ | 24 | 99.9% | Common in jewelry |
| 23K | 23 | 95.8% | Regional / specialty |
| 22K | 22 | 91.7% | Common in jewelry |
| 21.6K | 21.6 | 90.0% | Regional / specialty |
| 21K | 21 | 87.5% | Regional / specialty |
| 20K | 20 | 83.3% | Regional / specialty |
| 19K | 19 | 79.2% | Regional / specialty |
| 18K | 18 | 75.0% | Common in jewelry |
| 16K | 16 | 66.7% | Regional / specialty |
| 15K | 15 | 62.5% | Regional / specialty |
| 14K | 14 | 58.3% | Common in jewelry |
| 12K | 12 | 50.0% | Regional / specialty |
| 10K | 10 | 41.7% | Common in jewelry |
| 9K | 9 | 37.5% | Regional / specialty |
| 8K | 8 | 33.3% | Regional / specialty |
Unmarked gold
If there is no stamp, use an acid test kit or XRF at a reputable jeweler before selling. Guessing karat can undervalue or overvalue a piece by a wide margin.