You should definitely check out the latest Atavist book, The Devil Underground, by Nadja Drost. 
Drost provides the clearest insight I’ve ever encountered regarding the conflict for Antioquia involving the Urabeños and the Rastrojos. She demonstrates herself as a fearless, serious journalist dedicated to uncovering the truth behind stories. Moreover, she enlightens readers about the true cost of gold, especially Colombian gold. This book also stands out as one of the most exquisite literary nonfiction works I’ve come across in ages. I’ve been diving deep into information about Gran Colombia Gold, which aims to transform Segovia into a conventional professional mining operation. After following this situation for years, I now feel significantly closer to grasping it all—despite the book hardly mentioning Gran Colombia. It’s well worth your US$3.99. Go check it out.
UPDATE: I just noticed this article, which indicates that a connection between crime and gold might still exist in Colombia.