Peridotite is an umbrella term for phanertic, plutonic, ultramafic igneous rocks that are characteristically abundant in olivine and typically occur with amphibole and pyroxene. Descriptors, such as phaneritic, plutonic, and ultramafic provide a visualization of a dense, coarse-grained, and dark-coloured rock, but also interprets the slow and intrusive crystallization and extremely silica-poor, magnesium and iron-rich composition. The International Union of Geological Sciences (IUGS) uses a ternary classification diagram specific for such coarse-grained ultramafics with modes based on the abundance of olivine, orthopyroxene, and clinopyroxene. This diagram divides into pyroxenites and peridotites, showing their subtypes and modal compositions. Peridotite subdivides into four types: lherzolite, harzburgite, wehrlite, and dunite. Lherzolite comprises the larger range of model combinations of olivine, clinopyroxene, and orthopyroxene central of the diagram, while harzburgite and wehrlite are located along the legs of the diagram, both generally having the same range of olivine abundance, but harzburgite being the orthopyroxene-rich, clinopyroxene-poor subtype while wehrlite being the latter. In contrast, dunite is particularly specific in composition, taking up a single corner of the diagram, comprising the greatest abundance of olivine (>90%). Due to these combinations of minerals, peridotites are typically dark-coloured or distinctly green, like the sample above. Peridotites bear great significance as they are economically resourced for diamonds and chromite and they are dominant in the composition of the Earth's upper mantle, making its surface exposure a phenomenon of tectonic processes. It is theorized that peridotites ascend to the Earth's surface by transport through deep-source magmatic structures, such as ophiolites, pipes, or dike and sill intrusions. However, its exposure to the surface makes its extremely high-temperature minerals unstable, often undergoing weathered or hydrothermal alteration into minerals, like calcite, magnesite, chlorite, talc, and serpentinite. Additonally, these alteration minerals can also be sourced economically or for natural carbon sequestration.