Yixing is a county-level city under the jurisdiction of Jiangsu Province, which is managed by Wuxi City, and the product quality supervision and inspection office in the city can identify the authenticity.
If you just want to test the purity of the jewelry you bought, you can also ask the other party to help you with the identification in the name of recycling and replacement in the larger local jewelry and silver shop sales organization. Generally, there will be relevant testing instruments and equipment.