An igneous rock consisting dominantly of mafic mineral, containing tiron and magnesium and with much less silicon and aluminum than most crustal rocks. Most come from the Earth's mantle. Includes dunite, peridotite, amphibolite, and pyroxenite.
An igneous rock composed entirely of ferromagnesian minerals.
An igneous rock consisting almost entirely of Fe- and Mg- rich minerals, with virtually no quartz or feldspar, and silica contents typically less than 45%.
Typically, dark coloured rocks that have been intruded into the Earth or extruded underwater in a marine environment. May have been altered by heat and pressure producing foliation in the rock. They can be low strength, sheared and altered and a potential source of challenging ground conditions.
An igneous rock consisting almost entirely of of ferromagnesian minerals, i.e. iron- and magnesium-rich minerals. The silica content is typically less than 45%.
Igneous rock composed chiefly of dark-colored ferromagnesian silicate minerals. Asbestiform amphiboles, when found, can occur in localities with ultramafic rock.
An igneous rock composed of mainly olivine and pyroxene; it forms an important part of oceanic crust.
very dense rock which is very poor in free quartz (SiO2) and very rich in iron (Fe) and magnesium (Mg). These rocks characterize the earth's mantle.
Ultramafic (or ultrabasic) rocks are igneous and meta-igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is considered to be composed of ultramafic rocks.