Pumpellyite - Ca₂Al₂(Al,Fe³⁺Fe²⁺Mg)1.0[Si₂(O, OH)_7>][SiO₄](OH, O)₃

Named in 1925 by Charles Palache and Helen E. Vassar in honor of US geologist, Raphael Pumpelly. Pumpellyite is a nesosilicate containing both independent SiO^4- tetrahedral and Si₂O₇^6- units cross-linking octahedral chains occupied by metals. Pumpellyite, is chemically and structurally related to epidote group minerals. Pumpellyite occurs as amygdaloidal and fracture fillings in basaltic and gabbroic rocks in metamorphic terranes. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies. It is associated with chlorite, epidote, quartz, calcite and prehnite

Optical properties:

• Form: Acicular, fibrous or bladed crystals.
• Color: pale green or yellow.
• Relief: moderate.
• Interference colors: low II order often with anomalous blue colors.

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Green, massive prehnite crystals. Mohave County, Arizona, USA. From RRUFF.

Colorless bladed prehnite crystals. Eagle Head (Deep Cove), Cape Breton County, Nova Scotia, Canada. From RRUFF.

Colorless bladed prehnite crystals. Eagle Head (Deep Cove), Cape Breton County, Nova Scotia, Canada. 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
Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)
Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and interstitial white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic, high relief Pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 2x (Field of view = 7mm)	Prismatic, high relief Pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals in a gabbro. Tuscany (Italy). PPL image, 10x (Field of view = 2mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 10x (Field of view = 2mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)
Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)	Prismatic pumpellyite crystals (blue) and white-yellow prehnite crystals in a gabbro. Tuscany (Italy). XPL image, 2x (Field of view = 7mm)