4.5" Peridot in Basalt - Arizona

Peridot is a magnesium iron silicate mineral with the basic chemical formula Mg2SiO4. It is a gem variety of the mineral forsterite, and ranges between yellow, olive, and brownish green depending on the amount of iron present during formation. Dark, olive green-colored peridot gems are typically the most sought after. Peridot was originally named as topaz and was used for a variety of reasons, whether it be during the Crusades as a way to adorn religious objects, or even thought by many to posses medicinal powers. For unknown reasons, the original name was removed and given to the mineral that most know as topaz today, sometime during the 18th century.

Many gem-quality specimens were originally in basalt nodules in the Earth's mantle, and were fragmented and brought to the surface by volcanic activity.