Aventurine is a form of chalcedony (quartz) that contains small inclusions of various shiny minerals. These materials, usually spangles of mica or iron oxide, give the stone a glistening effect known as aventurescence. Aventurine's granular appearance and particular translucence are its most distinctive characteristics. Most aventurine is naturally reddish brown or yellow, though a green variety is also known. The green aventurine you'll find on the market, as well as the red and blue, is almost certainly dyed to achieve its color.
The mineral aventurine is named for its resemblance to the well-known aventurine glass of Venice, Italy. As for how the glass obtained its name, tradition has it that a Murano workman accidentally dropped some copper filings in molten glass, creating an attractive new material. And so the glass was named avventurino for the Italian word avventura, or "by chance."
Aventurine is said to calm a troubled mind, thereby bringing inner peace. It is also supposed to increase confidence and gratitude, and promote emotional tranquility and positive attitudes. Aventurine is found in Brazil, China, Japan, Russia, Tanzania and the U.S.A., but India produces the majority.