Lignum nephriticum cup product of narra wood (the namesake on the province) made opalescent hues when water is poured into it. These wood cups had been A serious pre-colonial and colonial industry of Naga. Naga would be the indigenous pre-colonial title of town. It's named following the narra tree https://devinlzlxh.wizzardsblog.com/28192957/23naga-things-to-know-before-you-buy