How can people check if the gold jewellery they buy on Dhanteras is real?

Indians usually buy jewellery to mark Dhanteras, which is being celebrated today. To check the purity of gold jewellery, people must look for BIS hallmark, check the caratage or fineness marking and verify HUID using the BIS Care app. For diamond jewellery, people must ask for a relevant grading report and check the characteristics it records.