Prehnite - Ca2(Al,Fe3+)[AlSi3O10](OH)2

Named in 1788 by Abraham Gottlieb Werner in honor of the Dutch Colonel, Hendrik von Prehn, who is credited with discovering the mineral in 1774 at the Cape of Good Hope in South Africa. Prehnite is a secondary or hydrothermal mineral and commonly lines cavities in igneous rocks. It also occurs as stalactite masses.

Optical properties:
• Form: Include nodular, concretionary, radial, encrusting and stalactitic formations among other similar types.
• Color: Colorless in thin section.
• Interference colors: Anomalous colors (blue, yellow, violet, red).
• Relief: Low



prehnite2020(1).jpg

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




prehnite2020(2).jpg

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




prehnite2020(3).jpg

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
phrenite2015(1).jpg

Colorless prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). PPL image, 2x (Field of view = 7mm)		 phrenite2015(2).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(3).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite2015(4).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(5).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(6).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite2015(7).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(8).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(10).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite2015(11).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(12).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(14).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite2015(15).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(16).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(17).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)
phrenite2015(18).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(19).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(20).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)
phrenite2015(21).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(22).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(23).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)
phrenite2015(24).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). PPL image, 10x (Field of view = 2mm)		 phrenite2015(25).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(26).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)
phrenite2015(27).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(28).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)		 phrenite2015(29).jpg

prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 10x (Field of view = 2mm)
phrenite2015(31).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(32).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(33).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite2015(34).jpg

Radial aggregates of prehnite crystals in a altered basalt. visible, in black, the original basalt. Loanhead Quarry (Scotland). PPL image, 2x (Field of view = 7mm)		 phrenite2015(35).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)		 phrenite2015(37).jpg

Radial aggregates of prehnite crystals in a altered basalt. Loanhead Quarry (Scotland). XPL image, 2x (Field of view = 7mm)
phrenite(1).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. PPL image, 1x (Field of view = 9mm)		 phrenite(2).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(3).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)
phrenite(4).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(5).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(6).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. PPL image, 1x (Field of view = 9mm)
phrenite(7).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(8).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(9).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. PPL image, 1x (Field of view = 9mm)
phrenite(11).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 1x (Field of view = 9mm)		 phrenite(12).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite(13).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)
phrenite(14).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite(15).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite(16).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)
phrenite(17).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite(19).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite(21).jpg

Radial aggregates of prehnite crystals in a altered basalt. Olbicella, Piemonte, Italy. XPL image, 2x (Field of view = 7mm)
phrenite2017(2).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(4).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(5).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)
phrenite2017(6).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(7).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(9).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)
phrenite2017(10).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(15).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(16).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)
phrenite2017(17).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(18).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(19).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)
phrenite2017(20).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(21).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)		 phrenite2017(22).jpg

Radial aggregates of Prehnite and calcite crystals in a altered peridotite. Orcistico, Pisa province, Tuscany, Italy. XPL image, 2x (Field of view = 7mm)