Noun
rock hound (plural rock hounds)
(idiomatic) A person who collects rocks and minerals from the natural environment as a hobby.
By the age of seven, Geoff was already an avid rock hound, fossil collector and amateur astronomer. Source: Internet
Handcrafted in Pittsburgh, PA by Dani Barbe: former rock star turned rock hound who sculpts and sets gemstones and minerals into fashion-forward statement pieces. Source: Internet