Most tough has patches or veins with the host rock in which it formed, which include chalcedony, opal, brown limonite, black chert, or white kaolinite. Lapidaries often Slash this brownish or black matrix along with the stone to deliver color contrast and styles. sapphire found out tanzanite in 1967 in https://www.gemsbiz.com/blog/explore/the-december-birthstone-zircon-tanzanite-turquoise