Where can I identify gold in Yibin? Why does the gold jewelry of Tianxin Diamond City have no qualified certificate?

I bought a golden necklace in Yibin Tianxin Diamond City. Only the invoice and there was no qualified certificate. I don't know if this is a regular. Essence I want to do an appraisal, but I do n’t know where to do it. Do you know that you can tell me?