GY 302: Crystallography and Mineralogy (2011) Assignment 2: Stereonet projections Your Task: One last session with crystallography and then we are done. I would like you to plot the faces of three model crystals (4, 75, 167) on three separate stereonets (Wulff nets). One of the models is an isometric crystal, one is tetragonal and one is orthorhombic. Here are the rules for plotting the crystals: To find the points 1) position the crystal with the c-axis up above the Wulff net. For tetragonal crystals, this is the longest axis. For orthorhombic crystals it is normally the shortest axis, but for the model that you will encounter this year, position the model with the A2 axis up. For isometric crystals, all axes are the same length so it doesn’t matter which is up. 2) Any face that lies exactly 90° to the plane of the Wulff net (e.g., (100), (001)) will haves its pole plot on the great circle that delineates the stereonet. Any face exactly parallel to the plain of the paper (e.g., (001)) will have its pole plot at the exact center of the Wulff net. 3) Use a contact goniometer to measure the angles between crystal faces*. These values will be used to determine where on the stereonet each pole plots. To plot the points 4) Poles that project downward into the Wulff net are shown with an open circle. Poles that project upward are shown with closed lines. Overlapping upper and lower pole intersections are shown with a solid dot inside of an open dot., You will be given an example on how to do this during a lecture slot. You will need a first make a contact goniometer and a stereonet base. Tracing paper will be provided. Due Date: See the calendar or website for due dates.Stereonet to be used for point group symmetry exercise (if possible print this on sturdy paper or light cardboard. Push a thumb tack from the back of the stereonet through the paper at the exact center of the plot. Use tape to adhere the tack to the back of the pageCut line Instructions: to make your own contact goniometer. 1) Print out this page on, if possible, sturdy paper or light card board. 2) Cut out the 2 pieces of the goniometer as close to the edges as possible. Be sure to make your cut along the bottom of the protractor component as parallel to the bottom edge as humanly possible. 3) Make a holes using a punch at the locations indicated by the circles in the protractor and pointer portions of the goniometer. 4) Using a fastener (available from Doug), attach the pointer to the protracter. 5) Measure away!How to use a contact goniometer to measure angles between crystal faces in wooden models (and
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