Trapiche Emeralds

Trapiche Emeralds

Trapiche gemstones are fascinating minerals that possess a star or spoke like pattern of inclusions which may or may not include a central core or hub. The most famous of the trapiche gemstones are the trapiche emeralds from Colombia; however many different minerals can exhibit trapiche patterns. Trapiche gemstones are incredibly rare and are coveted by collectors and jewelry designers for their unique appearance.

History

Trapiche (pronounced tra-pee-che) is the Spanish word for sugar mill and the spokes on the emerald resemble the grinding wheels used in the sugar mills. Trapiche mills were used in Colombia to extract sugar from sugarcane.

These emeralds were first mentioned at a meeting of the Société Géologique de France in 1897 by the French mineralogist Emile Bertrand.

Location

They are found in Colombia where many of the world’s finest emeralds originate and have been recovered on occasion from a small number of mines on the western side of the Eastern Cordillera Basin. Some specimens have also been recovered from Brazil.

Formation

They are older than normal Colombian emeralds and began their growing process during local decompression which was responsible for the supersaturation of fluid. Supersaturation occurs when a solution contains an excessive amount of solute particles which makes the solute separate itself from the solution and crystallize. The hydrothermal fluid came into contact with the black shale rocks present in the region and began to form emerald seed crystals.

During the formation of seed crystals, textural sector zoning (i.e., the accumulation of inclusions derived from the black shale rocks along the interfaces of growth sectors) occurred. This led to the development of the distinctive dendrites or spokes around the core and between the arms.

Black shale rocks contain lots of carbon based or transformed organic matter. The presence of transformed organic matter or graphite has been observed in trapiche minerals formed in different geological environments. It is believed that graphite can control the fluid composition and dictate the mechanism and timing of mineral growth. So, the presence of graphite and carbon-based inclusions may be necessary in the formation of all trapiche gemstones.