Green Aventurine 4mm Rnd (N) Green aventurine has a shimmering iridescence and a semi-translucent appearance. Aventurine is a metamorphic rock, meaning it is made up of more than one mineral. Green aventurine is mostly quartz with the glistening effect coming from tiny inclusions of shiny mica minerals. A beautiful polish and smooth finish. The alluring green tones vary slightly on each strand.