35 Minerals in Motion: Tracking Mineral Reactions Using In Situ and Synchrotron Techniques, A Celebration of the Career of Peter Heaney (Posters)

In celebration of the career of Dr. Peter Heaney, we invite submissions using in situ, synchrotron, X-ray, neutron, or electron techniques to study rates/mechanisms of mineral reactions, alongside contributions exploring new approaches to mineralogy education.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

The Effect of Crystal Orientation on the Raman Spectra of K-Feldspar Polymorphs

Paper number: 35-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

  • Ellie Kanz Presenting Author
    University of Alaska Fairbanks, Fairbanks, AK
  • Marisa Acosta
    University of Alaska Fairbanks, Fairbanks, AK

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 Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412300

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