Presentation Information
[O12-P11]Quantitative Analysis of Angle-Dependent Labradorescence Intensity
Using a Custom 360° Scanning System
*Wakana Tanaya1 (1. Yokohama Science Frontier High School)
Keywords:
Labradorescence,Angle of Maximum luminance,FWHM
Labradorescence is a well-known structural color of Labradorite, but its angle-dependent brightness and directionality have not been studied in a systematic way.
In this study, we focused especially on differences in structural color and on differences between polished and unpolished surfaces. We developed a custom 360° scanning system to measure the intensity of Labradorite at different angles.
Four samples were used: A (blue, polished), B (red, polished), C1 (yellow, polished), and C2 (multicolored, unpolished).
The back side of sample A (black) was used as a reference for setting the brightness threshold.
All samples were measured under the same conditions in a dark room.
Images were taken every 5° or 10°, and intensity was calculated from RGB values using “ImageJ”.
Three indicators were used for analysis: peak angle, full-width at half-maximum (FWHM), and maximum luminance.
Sample A showed strong emission with a FWHM of about 30°.
Sample C (polished) showed high directionality with a FWHM of 27°.
Sample B showed weaker emission but had a clear peak.
In contrast, the unpolished surface of sample C showed a broad angular distribution (FWHM 103°) with multiple peaks caused by surface roughness.
The three polished samples had similar FWHM values (27–30°), and no clear relationship was found between maximum luminance and FWHM.
Additional tests showed good reproducibility, little dependence on ROI size, and good agreement between RGB components and luminance.
These results demonstrate that the custom 360° scanning system can reliably evaluate the angle dependence of Labradorescence.
This method is useful for analyzing structural colors and can be applied to other minerals.
In this study, we focused especially on differences in structural color and on differences between polished and unpolished surfaces. We developed a custom 360° scanning system to measure the intensity of Labradorite at different angles.
Four samples were used: A (blue, polished), B (red, polished), C1 (yellow, polished), and C2 (multicolored, unpolished).
The back side of sample A (black) was used as a reference for setting the brightness threshold.
All samples were measured under the same conditions in a dark room.
Images were taken every 5° or 10°, and intensity was calculated from RGB values using “ImageJ”.
Three indicators were used for analysis: peak angle, full-width at half-maximum (FWHM), and maximum luminance.
Sample A showed strong emission with a FWHM of about 30°.
Sample C (polished) showed high directionality with a FWHM of 27°.
Sample B showed weaker emission but had a clear peak.
In contrast, the unpolished surface of sample C showed a broad angular distribution (FWHM 103°) with multiple peaks caused by surface roughness.
The three polished samples had similar FWHM values (27–30°), and no clear relationship was found between maximum luminance and FWHM.
Additional tests showed good reproducibility, little dependence on ROI size, and good agreement between RGB components and luminance.
These results demonstrate that the custom 360° scanning system can reliably evaluate the angle dependence of Labradorescence.
This method is useful for analyzing structural colors and can be applied to other minerals.