Zoisite - Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)

Zoisite, first known as saualpite, after its type locality, isa sorosilicate belonging to the epidote group of minerals. Named after Sigmund Zois, Baron von Edelstein (1747-1819), Austrian scholar who financed mineral-collecting expeditions. Ionic substitution in zoisite is very limited; Al³⁺ may be replaced by Fe³⁺ ore Cr³⁺ and lesser amount of Mn³⁺ may be present. Even very minor Mn³⁺ produces intense pink color, forming the poorly defined variety Thulite.

The most common occurrence of Zoisite is in schists and granulites of medium-grade regional metamorphism. Is a common minerals also in contact aureoles with calcite, idrocrase and grussular. Zoisite is a common hydrothermal product of Ca-Rich plagioclase where it appears in a fine-grained mass, in association with muscovite, calcite or chlorite, called Saussurite.

Optical properties:

• Form: Prismatic
• Color: Colorless to pale yellow
• Relief: High
• Cleavage: Perfect basal cleavage (001)
• Interference colors: Low (blue)

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
Zoisite crystal with blue interference colros. XPL image, 2x (Field of view = 7mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Small Zoisite crystals (with blue interference colros) on plagioclase. XPL image, 10x (Field of view = 2mm)	Small Zoisite crystals (with blue interference colros) on plagioclase. XPL image, 10x (Field of view = 2mm)	Small Zoisite crystals (with blue interference colros) on plagioclase. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros and chlorite crystals. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros and chlorite crystals. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros and chlorite crystals. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 20x (Field of view = 1mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)	Zoisite crystals with blue interference colros. XPL image, 10x (Field of view = 2mm)
Zoisite and chlorite (gray) crystals in a chlorite-schist. XPL image, 20x (Field of view = 1mm)	Zoisite and chlorite (gray) crystals in a chlorite-schist. XPL image, 20x (Field of view = 1mm)	Zoisite and chlorite (gray) crystals in a chlorite-schist. XPL image, 20x (Field of view = 1mm)
Zoisite and chlorite (gray) crystals in a chlorite-schist. XPL image, 20x (Field of view = 1mm)	Zoisite and chlorite (gray) crystals in a chlorite-schist. XPL image, 20x (Field of view = 1mm)	Zoisite (blue interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)
Zoisite (blue interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)	Zoisite (blue interference colors) and pyroxene crystals in a skarn. XPL image, 1x (Field of view = 9mm)	Zoisite (blue interference colors) and vesuvianite (grey interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)
Zoisite (blue interference colors) and vesuvianite (grey interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)	Zoisite (blue interference colors) and vesuvianite (grey interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)	Zoisite (blue interference colors) crystals in a skarn. XPL image, 1x (Field of view = 9mm)
Zoned zoisite (blue interference colors) crystal in a skarn. XPL image, 2x (Field of view = 7mm)	Zoned zoisite (blue interference colors) crystal in a skarn. XPL image, 10x (Field of view = 2mm)

Metamorphic Minerals

Texture and Microstructure

Metamorphic Rocks

Zoisite - Ca2Al3(SiO4)(Si2O7)O(OH)

Zoisite - Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)