The most beautiful type of lapis lazuli is an opaque stone of a magnificent deep blue colour. Some stones contain flickering iron pyrites. The fewer of these inclusions there are, the more valuable the stone. Since lapis lazuli is very sensitive, it is advisable to take off a lapis lazuli ring when doing housework. Lapis lazuli was already known and popular in ancient times and was used for cutting signet rings. The main place of discovery is in the western Hindu Kush Mountains in Afghanistan, Siberia and Chile.