Colombian Trapiche Emeralds: Recent Advances in Understanding Their Formation

Colombia is the traditional source of the world’s finest emeralds, including the famed trapiche crystals, their distinctive texture resembling a wheel with six spokes. This gemological curiosity, found exclusively the black shales of the country’s western emerald zone, is linked to the peculiar structural of the deposits. The study presents a review and update on Colombian trapiche emeralds, followed a three-dimensional examination of the crystals combined with spectroscopic and chemical . The proposed formation model incorporates the structural geology of the deposits with the of trapiche and non-trapiche emeralds. The fluid accumulation at the faults’ tip in the black leads to maximum fluid overpressure and sudden decompression and formation of the emeraldbearing system. The authors show that trapiche emerald growth starts at the beginning of the decompression is responsible for local supersaturation of the fluid. The hydrothermal fluid comes in with the black shale matrix, favoring the formation of emerald seed crystals. During the growth these seeds, textural sector zoning occurs, sometimes associated with chemical sector zoning, along displacement of the matrix. Displacement growth occurs because the emeralds continue their , pushing the matrix material away from the growing faces. An overgrowth, generally of gem , can form after decompression, surrounding the core, the arms, and the dendrites, restoring the ’ euhedral habit.