Parisite has been reported in the Colombian Western emerald belt since the 18th century. Due to emeralds, many studies have been done in the area, showing the frequent association of this mineral with fluorite and emeralds. A physicochemical model is developed for the association of REE minerals revealing the fluorine activities under they were formed, key conditions to understand the evolution of the hydrothermal system (ie aF=-1, 5 to-4, 9).