Horsetail inclusions are usually made of two minerals: a tiny opaque crystal that is the focal point, and chrysotile, which flares out from it, creating the appearance of a horsetail. Photo: John I. Koivula/GIA.
Horsetail inclusions are usually made of two minerals: a tiny opaque crystal that is the focal point, and chrysotile, which flares out from it, creating the appearance of a horsetail. Photo: John I. Koivula/GIA.