Sugilite- KNa2(Fe,Mn,Al)2Li3Si12O30

Sugilite (also known as lavulite) is a relatively rare pink to purple cyclosilicate mineral with the complex chemical formula KNa2(Fe,Mn,Al)2Li3Si12O30. The crystals are rarely found and the form is usually massive. Sugilite was first described in 1944 by the Japanese petrologist Ken-ichi Sugi (1901–1948) for an occurrence on Iwagi Islet, Japan, where it is found in an aegirine-syenite intrusive stock. It is found in a similar environment at Mont Saint-Hilaire (Canada) and Apuane Alps (Italy).

Optical Properties:
• Form: Granular - Generally occurs as anhedral to subhedral crystals in matrix.
• Relief: Low.
• Color: Brownish yellow, Violet, Reddish violet, Pale pink.
• Pleochroism: Weak.

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Fibrous spheres and layer of sugilite (purple color) crystals. Kalahari manganese field, Northern Cape Province, South Africa. From RRUFF.




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Fibrous sugilite crystals (purple color). Kalahari manganese field, Northern Cape Province, South Africa. From RRUFF.




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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Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 2x (Field of view = 7mm)		 suugilite(3).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 2x (Field of view = 7mm)		 suugilite(4).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 2x (Field of view = 7mm)
suugilite(5).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 2x (Field of view = 7mm)		 suugilite(6).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)		 suugilite(7).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)
suugilite(8).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)		 suugilite(9).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)		 suugilite(10).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)
suugilite(11).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)		 suugilite(12).jpg

Pink sugilite crystals in a Mn mineralization from Vagli (Apuan Alps, Italy). PPL image, 10x (Field of view = 2mm)		 suugilite(13).jpg

Sugilite crystals (with low birefringence) in a Mn mineralization from Vagli (Apuan Alps, Italy). The gray crystals are quartz. XPL image, 10x (Field of view = 2mm)