Aventurin

Aventurin or avanturin glass was formerly made only in the Island of Murano, near Venice, but is now prepared throughout Germany, Italy, Austria, and France. It is a brown glass mass in which crystalline spangles of metallic copper according to [Friedrich] Wöhler (of protoxide of copper according to [Max Joseph] von Pettenkofer) appear dispersed. [...] The Bavarian and Bohemian glass-houses produce an aventurin glass rivalling the original.

Aventurin is also the name of a variety of quartz spangled with mica or other shiny mineral. A variety of spangled feldspar, found especially in Russia, and when polished used as a gem and highly prized, is also called Aventurin or popularly "sunstone".