Birefringence
Andrew Barlow
An interactive Michel-Lévy interference color chart that features a database of 562 minerals. Click on your observed color and section thickness, and the birefringence of your section will be automatically calculated, and candidate minerals will be suggested. The range of the chart can be be set to between 200 nm and 2500 nm. The chart can be offset by + or - λ, + or - λ/4. The chart can be used as a traditional nomogram, or displayed in a "simple" mode without the clutter of radial lines (which are no longer necessary on an interactive chart). Based on the methods of Sørensen (2013), the colors in the chart are a much truer representation of the colors seen at the microscope eye pieces than existing printed nomograms. The app includes optical and physical characteristics of candidate minerals including birefringence (minimum, maximum and mean), relief, optical character, pleochroism, color and cleavage. The app includes the Raith-Sørensen color chart, which is also interactive. The Raith-Sørensen chart is a direct representation of interference color as a function of birefringence and sample thickness (Sørensen 2013). A useful utility for polarized light microscopy, polariscopy, optical mineralogy, stress optics, or anyone with an interest in birefringent materials.
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