Metamorphic Minerals

Texture and Microstructure

Metamorphic Rocks

Glaucophane - Na₂Mg₃Al₂(Si₄O₁₁)₂(OH)₂

Glaucophane, From the Greek (glaukos) for "sky-blue" and (phainestai) "to appear" in allusion to its colour, belongs to the Glaucophane-riebeckite-crossite series; Ideal glaucophane, Na₂Mg₃Al₂(Si₄O₁₁)₂(OH)₂, forms at least major solid solution, with magnesioriebeckite, Na₂Mg₃Fe₂³⁺(Si₄O₁₁)₂(OH)₂, and riebeckite Na₂Fe₃²⁺,Fe₂³⁺(Si₄O₁₁)₂(OH)₂.

Glaucophane is a metamorphic mineral, obviously characteristic of, but non strictly restricted to the glaucophane schist facies (blueschist facies), wich, in turn, implies low temperature, high pressure metamorphism.

Optical properties:

• Form: Acicular to columnar crystals.
• Color: Blue
• Pleochroism: From blue to violet.
• Relief: Moderate.
• Cleavage: Typical amphibole cleavage intersect at about 58° and 122°.
• Interference colors: Low, from I order to II order.

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Blackish-blue fibrous aggregate of glaucophane crystals,Cazadero, Sonoma County, California, USA. From RRUFF.

Black, prismatic crystals of glaucophane in a calcite matrix, La Beaume, near Turin, Piedmont, Italy. 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.

Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals and rectangular, yellow Lawsonite crystals, Milos (Greece). XPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals and rectangular, yellow Lawsonite crystals, Milos (Greece). XPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals and rectangular, yellow Lawsonite crystals, Milos (Greece). XPL image, 2x (Field of view = 7mm)	< Glaucophane crystals, Milos (Greece). XPL image, 2x (Field of view = 7mm)
Glaucophane crystals and rectangular colorless lawsonite crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane crystals and rectangular colorless lawsonite crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)
Glaucophane crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane crystals and rectangular colorless lawsonite crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)
Glaucophane crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane (basal section) crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)	Glaucophane crystals, Milos (Greece). PPL image, 10x (Field of view = 2mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)	Glaucophane crystals, Milos (Greece). PPL image, 2x (Field of view = 7mm)
Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. XPL image, 2x (Field of view = 7mm)
Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. XPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. PPL image, 10x (Field of view = 2mm)
Glaucophane crystals in a quartz schist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a quartz schist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a quartz schist. PPL image, 10x (Field of view = 2mm)
Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. XPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)
Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. XPL image, 2x (Field of view = 7mm)	Glaucophane crystals in a quartz schist. PPL image, 2x (Field of view = 7mm)
Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)
Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)	Glaucophane crystals in a blueschist. PPL image, 10x (Field of view = 2mm)
Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). PPL image, 2x (Field of view = 7mm)	Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). XPL image, 2x (Field of view = 7mm)	Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). PPL image, 2x (Field of view = 7mm)
Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). PPL image, 2x (Field of view = 7mm)	Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). PPL image, 2x (Field of view = 7mm)	Glaucophane (blue) crystals in a blueschist from Ghinivert (Alpi del Monginevro; Alpi Cozie). PPL image, 2x (Field of view = 7mm)

Metamorphic Minerals

Texture and Microstructure

Metamorphic Rocks

Glaucophane - Na2Mg3Al2(Si4O11)2(OH)2

Glaucophane - Na₂Mg₃Al₂(Si₄O₁₁)₂(OH)₂