1. Contact the seller: First, contact the seller directly when buying jewelry, explain the weight inconsistency you found and ask them to provide an explanation.

2. Check the certificate and guarantee: carefully check the information on the appraisal certificate and quality guarantee to confirm whether there is a clear error explanation or correction record.

3. Request re-inspection: If the seller can't give a satisfactory explanation, you can ask them to arrange re-inspection or provide appraisal services from a third-party authoritative testing organization.

4. Legal consultation: If the seller refuses to cooperate, you can consult a legal professional to understand your consumer rights and explore possible legal actions.

5. Consumer protection organizations: If you think your rights and interests have been violated, you can complain to the local consumer protection organizations and seek their help and intervention.

6. Public exposure: If the above methods can't solve the problem, you can consider public exposure through social media or consumer forums to attract the attention of the public and relevant departments.

You should make sure that you have enough evidence and keep a record of communication, which may be very important for your rights protection.

I hope my answer can help you.