35-4 The Effect of Crystal Orientation on the Raman Spectra of K-Feldspar Polymorphs
Session: Minerals in Motion: Tracking Mineral Reactions Using In Situ and Synchrotron Techniques, A Celebration of the Career of Peter Heaney (Posters)
Poster Booth No.: 333
Presenting Author:
Ellie KanzAuthors:
Kanz, Ellie1, Acosta, Marisa D.2(1) Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, USA, (2) Department on Geosciences, University of Alaska Fairbanks, Fairbanks, AK, USA; Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA,
Abstract:
As Al/Si site disorder increases, the character and number of K-feldspar Raman peaks within the 280-290 cm-1 range systematically changes. However, similar peak widening effects are known to be caused by orientation differences, since molecular vibrations may be Raman “inactive” at certain orientations where they lack polarizability. Orienting samples so that the Raman beam is either parallel or perpendicular to the c-axis allows us to compare both. Raman spectra between microcline, orthoclase, and sanidine along <100> and spectra from different directions in the same crystal. Analysis with a 514nm laser at 50x magnification shows systematic differences both between the Raman spectra of different polymorphs at the same orientation and between those of similar polymorphs at different orientations. Nearly all peaks widen by 2-10 cm-1 when oriented perpendicular instead of parallel. The largest peak, 511 cm-1 for sanidine and 513 (+/-1) cm-1 for microcline and orthoclase, widens by less than 1 cm-1. Sanidine has two peaks at 474 and 511 cm-1 which are higher in intensity when oriented perpendicular to the c-axis than when oriented parallel. Microcline and orthoclase both have three peaks at 453, 474, and 513 (+/-1) cm-1. These peaks are thought to correspond to the T-O-T structures affected by disorder level. Microcline has widths of 9-11 cm-1. Orthoclase has much lower intensities and widths typically of 11-15 cm-1. Orienting microcline parallel to the c-axis decreases intensity of the 553 cm-1 peak and increases intensity of the 474 and 513 cm-1 peaks.
Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025
doi: 10.1130/abs/2025AM-6331
© Copyright 2025 The Geological Society of America (GSA), all rights reserved.
The Effect of Crystal Orientation on the Raman Spectra of K-Feldspar Polymorphs
Category
Discipline > Mineralogy/Crystallography
Description
Session Format: Poster
Presentation Date: 10/19/2025
Presentation Room: HBGCC, Hall 1
Poster Booth No.: 333
Author Availability: 9:00–11:00 a.m.
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