Most emerald mining in Colombia takes place along the Eastern Andean ridge, to the north of Bogotá. The 45-minute guided tours (in English and Spanish) offer a good intro to the process, an exhibition of different types of emeralds, how quality is determined, and the different mines in Colombia where the best stones are being mined. There’s an emerald store, of course, at the end of the tour, though you’re better off buying elsewhere. This museum is on the 23rd floor of the Avianca Building.