Clinopyroxene - XYZ₂O₆

Optical properties:

• Colour and Pleochroism: Usually colourless, gray, pale green or pale brown, darker colours associated with Fe-rich varieties titanaugite is more distinctly coloured from brown/pink to violet.
• Form: Form stubby prisms elongate along the c-axis, basal sections are 4 or 8 sided and show two cleavages at 90.°
• Cleavage: Parallel to {110}, which intersect at 90°.
• Twinning: Simple and lamellar twins and composition planes, which in combination may form a herringbone pattern.
• Alteration: Commonly alter to uralite (a light coloured amphibole), or may alter to serpentine, chlorite, biotite, carbonates and /or other silicates.
• Relief: High positive.
• Distinguishing Features: Inclined extinction, higher birefringence, 2nd order interference colours, low 2V, optically positive in comparison with opx.

For structural characteristics and for the classification of the Pyroxene group of minerals see the page structural characteristics and classification

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.

Aegirine
Aegirine crystal in a pantelleritic ignimbrite. Pantelleria island, Italy. PPL image , 2x (Field of view = 7mm)	Aegirine crystal in a pantelleritic ignimbrite. Pantelleria island, Italy. PPL image , 2x (Field of view = 7mm)	Aegirine crystal in a pantelleritic ignimbrite. Pantelleria island, Italy. PPL image , 2x (Field of view = 7mm)
Augite crystal in a foidite, Cape Verde island. PPL image, 2x (Field of view = 7mm)	Augite crystal in a foidite, Cape Verde island. PPL image, 2x (Field of view = 7mm)	Twinnedd augite crystal in a foidite, Cape Verde island. PPL image, 2x (Field of view = 7mm)
Augite crystal in a foidite, Cape Verde island. PPL image, 2x (Field of view = 7mm)	Augite crystals in a foidite, Cape Verde island. PPL image, 2x (Field of view = 7mm)	Augite and nepheline (grey) crystals in a foidite, Cape Verde island. XPL image, 2x (Field of view = 7mm)
Augite and nepheline (grey) crystals in a foidite, Cape Verde island. XPL image, 2x (Field of view = 7mm)	Augite and nepheline (grey) crystals in a foidite, Cape Verde island. XPL image, 2x (Field of view = 7mm)	Pyroxene in basal section, Vulcano island, Italy. XPL image, 2x (Field of view = 7mm)
Pyroxene in basal section, Vulcano island, Italy. XPL image, 10x (Field of view = 2mm)	Pyroxene in basal section, Stromboli island, Italy. XPL image, 10x (Field of view = 2mm)	Pyroxene in basal section, Vulture volcano, Italy. PPL image, 10x (Field of view = 2mm)
Augite in a tephrite, Rhine graben, Germany. PPL image, 10x (Field of view = 2mm)	Twinned ugite in a tephrite, Rhine graben, Germany. XPL image, 10x (Field of view = 2mm)	Augite and leucite (colorless) crystals in a tephrite, Rhine graben, Germany. PPL image, 10x (Field of view = 2mm)
Twinned augite and leucite (isotropic) crystals in a tephrite, Rhine graben, Germany. XPL image, 10x (Field of view = 2mm)	Pyroxene in basal section, and colorless laucite crystals in a basanite. Latium, Italy. PPL image, 10x (Field of view = 2mm)	Pyroxene in basal section, and isotropic laucite crystals in a basanite. Latium, Italy. XPL image, 10x (Field of view = 2mm)
Twinned pyroxene crystal in a tephrite from Latium, Italy. XPL image, 10x (Field of view = 2mm)	Hourglass zoning in a pyroxene. Tephrite from Latium, Italy. PPL image, 10x (Field of view = 2mm)	Hourglass zoning in a pyroxene. Tephrite from Latium, Italy. XPL image, 10x (Field of view = 2mm)
Diopside crystals in a volcanic rock from Amiata volcano (Italy). PPL image , 2x (Field of view = 7mm)	Diopside crystals in a volcanic rock from Amiata volcano (Italy). PPL image , 2x (Field of view = 7mm)	Diopside crystals in a volcanic rock from Amiata volcano (Italy). PPL image , 2x (Field of view = 7mm)
Diopside crystals in a volcanic rock from Amiata volcano (Italy). PPL image , 2x (Field of view = 7mm)	Diopside crystals in a volcanic rock from Amiata volcano (Italy). XPL image , 2x (Field of view = 7mm)	Diopside crystals in a volcanic rock from Amiata volcano (Italy). XPL image , 2x (Field of view = 7mm)