Aventurine is the name of a semi-precious form of translucent microcrystalline quartz. The distinguishing feature of aventurine is the metallic fleck inclusion.
Folklore has it that aventurine glass was invented by accident when a Murano glass artist spilled copper filings into the glass batch. The glass that resulted from that happy mistake was named aventurine -- a ventura is Italian for by chance.
Ironically, the natural stone aventurine is named for the glass that mimics the stone's appearance.