Olivine and other grains. Le Tremblet Beach, Reunion Island, France.
Olivine is named for its olive-green color. It is almost exclusively found in dark-colored igneous volcanic rocks such as basalt, gabbro and peridotite. It is especially common near volcanic oceanic islands like Hawaii, the Galapagos, and on Alaskan islands.
Olivine is a common ortho-silicate mineral that is actually a mineral series, not a single mineral. Its iron and magnesium components can vary in proportion, substituting for one another in the crystal structure. This results in colors ranging from green to yellow green. Olivine tends to break down or weather quickly at the earth surface.
Gem-grade olivine is known as peridot, the August birthstone.