JX is the maker’s mark for the Le Vian jewelry company. It is a family-owned company with a long history, dating from the 15th century. They are famous for reinventing several fine jewelry categories. They did it through unique combinations of colors of diamonds, gems, and gold. They popularized the under-appreciated brown diamonds and deep-colored stones as Chocolate Diamonds. Le Vian also guarantees that their gems and diamonds are natural stones.