Lignum nephriticum cup made from narra wood (the namesake from the province) made opalescent colours when water is poured into it. These picket cups had been A significant pre-colonial and colonial market of Naga. Naga is the indigenous pre-colonial name of the city. It's named following the narra tree https://gunnerfugqb.blogstival.com/51778135/detailed-notes-on-23naga