Olivine

This is the mineral Olivine. It’s a common rock-forming mineral that belongs to the Silicate chemical family because it contains repeating chains of linked Silicon and Oxygen tetrahedra. These tetrahedra consist of a single, central Silicon atom surrounded by 4 Oxygen atoms. In Olivine’s case, these Silicon and Oxygen tetrahedra are bound to atoms of Magnesium or Iron. Olivine that contains Iron is called Fayalite and has the chemical formula FeSiO4, while Olivine that contains Magnesium is called Forsterite and has the chemical formula MgSiO4. Both varieties are collectively known as Olivine. The mineral exhibits a vitreous, or glassy luster and produces a white streak. It's a relatively hard mineral, ranking 6.5 to 7 on Mohs hardness scale, and has a specific gravity between 3.2 and 4.5. It does not exhibit any cleavage. Olivine constitutes over 50% of the rock in Earth’s upper mantle and is thus one of the planet’s most common minerals. It’s found in both intrusive and extrusive igneous rocks, especially at divergent oceanic plate boundaries and hot spots. Volcanism at these locations produces mafic lavas and pyroclastic flows that often contain Olivine. Since Olive rapidly weathers on Earth’s surface, it releases Iron or Magnesium into the soil. These are important metals that contribute to soil fertility and thus promote plant growth. You may have heard that volcanic soils are especially fertile. This is likely due to the mineral Olivine breaking down on Earth’s surface. In addition to its importance as a contributing variable to soil fertility, the mineral also has aesthetic appeal as a gemstone. If you were born in August, your birthstone is Peridot, which is simply the mineral Olivine cut and polished into a gem. This gemstone has been prized for millennia due to its olive-green color and adamantine luster.