It may be in a market known for fake goods, but Amy Lin's is the most reliable retailer of pearls of all colours and sizes. Freshwater pearls (from ¥80), including prized black Zhèjiāng pearls (from ¥1500), and saltwater pearls (from ¥200) are available here. The staff speak English and will string your selection for you. This place sells jade and jewellery, too.