ROCK & GEM FIELD GUIDE: Peridot

Peridot is the bright green gem-quality variety of the mineral forsterite, a magnesium silicate.

- DR. STUART MILLS & PAM FREEMAN

Large, Faceted Peridot 764 carats

Both are commonly referred to as “olivine,” which is intended to refer to samples with a composition between forsterite and fayalite (an iron silicate). While many gemstones can be found in multiple colors, peridot occurs in shades that range from yellow-green to olive or brownish-green. The gem’s green color is because of its iron content, with higher concentrations producing deeper hues.

How It Forms