Fundamental Minerals

Sialic Minerals

Feldspars

Feldspathoids

Quartz

Femic Minerals

Spodumene

Accessory Minerals

Rare Accessory

Alteration Products

Microstructures

Rocks

Jacupiranga complex

Wollastonite - CaSiO₃

Named in 1818 by J. Léman in honor of William Hyde Wollaston Norfolk, English chemist and mineralogist who discovered palladium (1804) and rhodium (1809) and invented the reflecting goniometer (1809). Wollastonite is a calcium inosilicate mineral. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or contact metamorphic rocks. Is a very rare mineral in some alkaline igneous rock associated with carbonatites.

Although it is a single-chain silicate, wollastonite is not a pyroxene. Wollastonite have a different type of infinite-chain structure, with three tetrahedra per unit cell arranged parallel to y (Fig.1), this repeat unit consisting of a pair of tetrahedra joined apex-to-apex as in the [Si₂O₇] group, alternating with a single tetrahedron with one edge parallel to the chain direction.

Fig.1: Tetrahedra arrangement within the chains in pyroxenes compared to wollastonite. From Wikipedia.

Optical Properties:

• Form: Columnar, bladed or fibrous.
• Color: Colorless.
• Relief: Moderate.
• Birefringence: Up to I order Red.

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
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (colorless) and wollastonite (pale brown basal section). Wollastonite-melilitolite, Colle Fabbri, Italy. PPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (colorless) and wollastonite (pale brown basal section). Wollastonite-melilitolite, Colle Fabbri, Italy. PPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)
Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)	Melilite (with anomalous, berlin-blue colors) and wollastonite (orange-yellow birefringence). Wollastonite-melilitolite, Colle Fabbri, Italy. XPL image , 2x (Field of view = 7mm)