Fassaite - K5Ca8(Si6O15)2(Si2O7)Si4O9(OH)*3(H2O)

The name fassaite was first introduced to describe a pyroxene from an augite syenite-limestone contact in the Fassa valley, Trentino, Italy, where it occurs in light to dark green crystals. Subsequently the name has been more generally used to describe the Al-rich and Na-poor pyroxenes commonly found in metamorphosed limestone and dolomites. Fassaite Is commonly associated with calcite, garnet, spinel, vesuvianite and humites.

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Green fassaite crystals, Val di Fassa, Trentino, Italy. Photo by Marco Ballati.



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Green fassaite crystals. Casa Collina Old Quarry, Pitigliano, Grosseto, Tuscany, Italy.





Bibliography



• Bucher, K., & Grapes, R. (2011). Petrogenesis of metamorphic rocks. Springer Science & Business Media.
• Fossen, H. (2016). Structural geology. Cambridge University Press.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Passchier, Cees W., Trouw, Rudolph A. J: Microtectonics (2005).
• Philpotts, A., & Ague, J. (2009). Principles of igneous and metamorphic petrology. Cambridge University Press.
• 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.
• Vernon, R. H. (2018). A practical guide to rock microstructure. Cambridge university press.


Photo
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Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 2x (Field of view = 7mm)		 fassaite(2).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(3).jpg

Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 2x (Field of view = 7mm)
fassaite(4).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(5).jpg

Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 2x (Field of view = 7mm)		 fassaite(6).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)
fassaite(7).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(8).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(9).jpg

Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 2x (Field of view = 7mm)
fassaite(10).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(11).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 2x (Field of view = 7mm)		 fassaite(12).jpg

Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 2x (Field of view = 7mm)
fassaite(18).jpg

Fassaite (colorless, high relief and fractured) and calcite crystals in a marble. Fassa Valley, Italy. PPL image, 10x (Field of view = 2mm)		 fassaite(19).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 10x (Field of view = 2mm)		 fassaite(20).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 10x (Field of view = 2mm)
fassaite(21).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 10x (Field of view = 2mm)		 fassaite(22).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 10x (Field of view = 2mm)		 fassaite(23).jpg

Fassaite (high birefringence) and calcite crystals in a marble. Fassa Valley, Italy. XPL image, 10x (Field of view = 2mm)