This cookie is set by GDPR Cookie Consent plugin. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category 'Functional'. The cookie is used to store the user consent for the cookies in the category 'Analytics'. These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. Similarly, Ca-rich compositions lie towards the right of the diagram, since clinopyroxene is the only mineral in the diagram that contains Ca. This is because pyroxenes stoichiometrically contain more silica than olivine. SiO 2-poor compositions lie close to the top vertex (dunite), whereas SiO 2-rich compositions occur at the base of the diagram. This diagram defines very well the first-order chemical variability of ultramafic rocks. ‘Olivine’ is specified in the name in pyroxenite varieties with an olivine content between 5 and 40% (e.g. Websterite: consisting of clinopyroxene and orthopyroxene.Ĭlinopyroxenite: with clinopyroxene > 90%. Orthopyroxenite: with orthopyroxene > 90%. Wehrlite: consisting largely of olivine and clinopyroxene. Lherzolite: a peridotite with olivine, orthopyroxene, and clinopyroxene. Harzburgite: consisting predominantly of olivine and orthopyroxene. Two broad fields are separated based on the modal content of olivine: peridotites (olivine > 40%) and pyroxenites (olivine 90%). For ultramafic rocks containing hornblende (extremely rare) the diagram below should be used instead. Most ultramafic rocks consist of the three minerals in this diagram: olivine, ferromagnesian pyroxene (orthopyroxene, enstatite), and calcium pyroxene (clinopyroxene, diopside). IUGS classification of ultramafic rocks with olivine, orthopyroxene, and clinopyroxene.

Pyroxene and feldspar ternary diagram