Justin K Prim is an American lapidary and gemologist living and working in Lyon, France. He has studied gemcutting traditions all over the world as well as attending gemology programs at GIA and AIGS. Justin has taught gemology and gemcutting at AIGS and IGT in Bangkok and he has recently published his first book, The Secret Teachings of Gemcutting.

He is the founder of Faceting Apprentice, an online gemcutting school, and he also writes articles, produces videos, and gives talks about gem cutting history.