Olivine is a rather unassuming rock. Olive brown to yellow green in color, this hard yet brittle mineral is thought to be the most abundant in Earth’s upper mantle. Chemically, olivine is magnesium iron silicate, though it contains other elements too. Economically, it’s close to worthless. Its limited industrial utility stretches to gemstones, metalworking, ceramics, and occasionally, as a gravel for road construction. At some mining sites, olivine is a waste product, stored in piles on the surf...