Trapiche gemstones

Trapiche-like rhodochrosite “flower.”  From GIA.

Trapiche-like rhodochrosite “flower.”  From GIA.

Trapiche is the Spanish word for a spoked wheel used to grind sugar cane. It is also a gemological term for a six-rayed spoke pattern that can occur in different minerals (best known in emeralds). "Trapiche-type" or "trapiche-like" refers to gems with a pattern that doesn't quite meets the standards for identifying a stone as trapiche. True trapiche gemstones are single crystals where the growth sectors are separated by inclusions.

Gems with trapiche patterns haven't been studied for all that long. The first mysterious six-spoked emeralds were sent to the Gemological Institute of America in the 1960s for analysis. (Before that they had been described by the French mineralogist Emile Bertrand in 1879.) But since then the family of trapiche-type gem minerals has grown to include a variety of species and morphologies. In addition to the famous and rare trapiche emeralds, adventurers and geologists have uncovered trapiche ruby, sapphire, garnet, chiastolite and tourmaline. There are also muscovite and rhodochrosite with the six-rayed pattern.  And pezzottaite!

Most of the images of trapiche and trapiche-type gemstones in the slideshow below are from the Gemological Institute of America.