Aventurine is a quartz with inclusions of mineral platelets which give it a glittery effect. The most common color is green, but it also comes in blue, brown, gray, orange, and yellow. Its name comes from the Italian "a ventura," meaning "by chance." This is a reference to the accidental discovery of aventurine glass in the 1700s.
According to The Golden Bough by Sir James George Frazer, the Lotuko, Bari, and Lokoya of South Sudan have used aventurine, quartz, and amethyst as rain stones in rain-bringing rituals.