Dunite is an ultramafic plutonic rock that is composed almost exclusively of olivine. “Ultramafic” means that mafic minerals form more than 90% on the rocks composition. Most common mafic minerals in ultramafic rocks are definitely pyroxenes and olivine (if hornblende is present it is added to pyroxenes). Rocks that contain more than 40% olivine are peridotites. Note that this 40% means 40% of olivine-pyroxene(hornblende) pair, all other minerals are excluded in current classification scheme. Attributes: 45% MgO High purity Uses: used to sequester CO2