Olivine is a precious gemstone which occurs in basalt, peridotite and other basic igneous rocks. It has an olive-green, grey-green appearance.

Unearth a family activity with a difference: crystal fossicking. Mount Shadwell Quarry at Mortlake allows fossicking for olivine, an olive-green, grey-green, or brown mineral found in basalt, peridotite, and other igneous rocks. Large volcano-ejected rocks, known as volcanic bombs, can contain olivine and make for a fun treasure hunt and very unusual souvenirs.