The gemstone variety of the mineral olivine is known as Peridot. Although olivine is actually a quite abundant mineral, gem quality Peridot can be rare and hard to find. Peridot is one of the few gemstones that naturally occur in only one color: green. Although the shade of green can vary from yellow-green to brown-green, the most valuable is considered to be the dark-olive green. These stones are mined in Arizona, Hawaii, Nevada, New Mexico and even North Carolina. Peridot is the birthstone for the month of August.