Eye Agate

Eye agate is defined by its pattern, not by a separate mineral: Mindat describes agate with concentric rings that look like an eye, lists "Aleppo stone" as a synonym and "bird's eye agate" as a sub-type, and gives the German names Augenachat and Augenstein. For the black-and-white 天眼石 beads sold in Japan, the report published by Pascle (laboratory: 日本彩珠宝石研究所) reads: natural quartz (polycrystalline), gem name black onyx, black opaque stone with white bands, colored by dye. The IGS notes that black onyx sold in stores is almost always dyed and that dyeing of chalcedony is common, usually stable, and should be disclosed.

As chalcedony, eye agate needs no special care; clean it with mild detergent, warm water and a soft brush. Dyeing of agate is usually stable.

According to Japanese retailers such as Pascle, the name 天眼石 refers to its eye-like pattern; they say it was first found in Tibet lying on the ground rather than buried, was therefore said to have fallen from heaven, and was long used for ritual objects and amulets, and they associate it with warding off evil. These are trade claims that independent sources read for this record do not document.