1. Using Matlab for Thin Section Analysis Sam DeNicola Fall Semester, 2014 EPS 109

2. EDU>> MineralAnalysis('hblendeplagiometals.jpg') How many different minerals are there in the rock sample? : 3 Name of 1 Mineral Species : Plagioclase Name of 2 Mineral Species : Hornblende Name of 3 Mineral Species : Opaque Metals Please estimate how many different distinct mineral colors there are in the rock sample in order to filter the image : 4 Creating filtered image for easier processing Please select the characteristic colors for Plagioclase and then press "Enter" Please select the characteristic colors for Hornblende and then press "Enter" Please select the characteristic colors for Opaque Metals and then press "Enter" Creating masks for images Creating isolated images of crystals of Plagioclase using the image mask... Creating isolated images of crystals of Hornblende using the image mask... Creating isolated images of crystals of Opaque Metals using the image mask... Method for analysis Read image input by user with Matlab function imread Allow for user input of number of minerals present in thin section, and number of distinct colors seen in the slide. Use number of colors to create a filtered image Have user select characteristic colors for each named mineral Iterate through the image checking each pixel’s RGB values against user’s selections Create BW image mask coloring all pixels white where the colors matched, leaving the rest black Slightly filter images to get rid of noise Count white pixels for data Use pixel count and Matlab functions to provide analysis Sample command line Background Minerals in thin section can have characteristic colors in plane polarized light. They also have characteristic ranges of birefringence colors in cross-polarized light that depend on the mineral grain orientation on the slide and the crystalline structure of the given mineral. Birefringence is defined as the difference between the largest and smallest refractive index of a mineral.

3. To run: Enter “MineralAnalysis(‘nameofyourimage.jpg’)” into the Matlab command line and then follow the on-screen directions Pictures by Kurt Hollocher http://minerva.union.edu/hollochk/c_petrology/