Hornblende-olivine-bearing pyroxenite

A pyroxenite is a basic igneous rock dominated by pyroxene, with up to 40% olivine, accessory phases can include plagioclase, spinel, garnet, ilmenite, chromite and magnetite. Pyroxenites dominated by orthopyroxene are termed orthopyroxenites, those dominated by clinopyroxene are known as clinopyroxenites, those with similar abundances of orthopyroxene and clinopyroxene are known as websterites. Pyroxenites are an important component of mantle rocks and are found within mantle xenoliths and within the mantle sequence of ophiolites, often occurring as veins and dykes. In the mantle pyroxenites are largely produced by crystallisation of partial melts. Pyroxenites also are found in layered intrusions where they form as cumulates.

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Pyroxene (dark) and rare plagioclase (white) crystals. Pyroxenite from Aurenhågån, Norway. From Hildegard Wilske

Pyroxene (dark) and rare plagioclase (white) crystals. Pyroxenite from Aurenhågån, Norway. From Hildegard Wilske

Pyroxene (dark) and rare plagioclase (white) crystals. Pyroxenite from Husebykollen quarry, Norway. From Hildegard Wilske

Pyroxene (dark) and rare plagioclase (white) crystals. Pyroxenite from Husebykollen quarry, Norway. From Hildegard Wilske

Bibliography

• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.

Photo
Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)
Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. XPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. XPL image. 2x (Field of view = 7mm)
Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. XPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)
Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)	Hornblende, clinopyroxene and olivine crystals in a Hbl-Pyroxenite. Antarctica. PPL image. 2x (Field of view = 7mm)