Ultramafics
These are high temperature rocks, meaning they form first; they contain the elements that crystallize out first, at the highest temperatures, such as Mg and Fe, and include high temperature plagioclases such as Anorthosite. They are classified according to the IUGS (International Union of Geologic Sciences) by their composition and relative abundances of Clinopyroxene (Cpx; pyroxenes containing calcium), Orthopyroxene (Opx; pyroxenes not containing calcium), and Olivine. (See Fig.2) A good understanding of the high temperature minerals can be obtained from Bowen’s Reaction Series. The ultramafics can be deformed, and is commonly serpentized, which refers to hydrothermal alteration of existing rock.
Ultramafic Samples:
More Pictures