Mineral Visualization Assignment

For each of the following minerals, visualize the crystal structure of the mineral using the Vesta crystal and sructural modeling software. This is installed on the geology dept comp lab, and should also be on the IQ Center and Parmly 302 lab machines. You can alternatively download it and install it on your own machine. It is free software.

You may discuss with other students, but you may not use other students images, visualizations, etc. That is, all of you are to do the assignment on your own, running the software yourself. You are not to use any students' previous work in this class.

Basic Directions: Find the .cif file that describes the mineral crystal structure. This can be obtained from from the American Mineralogist Crystal Structure Database. Choose the top search result, and download the .cif file.

Next load this into Vesta. Then manipulate the models and view in order to answer the questions posed.

These models come in as a unit cell. In each .cif file you bring in you will likely want to make the boundary range coordinates 2 or 3 (larger than just one unit cell), particularly when thinking about cleavage.

The default view is a “Ball and Stick” view where the ions are balls and the bonds are sticks. Click and hold the left mouse button to move the 3-D model around. The unit cell principal axes are shown as arrows. You can label the atoms, turn on and off atoms, bonds and polyhedra, and change the way each of these is displayed.

Your assignment is to visualize the crystal structure of the minerals, copy an image that best represents what you are trying to show and then paste it into a Powerpoint slide. Sometimes you might want a couple of images, but you would have to resize them in Powerpoint if you did that. Then answer the following questions about the mineral by choosing Insert-> Text Box and then typing the answer. Please answer in sentences. In most cases you will need to annotate the slide by drawing a line or an arrow from the drawing palette. You likely will not know ahead of time the answer to all of the questions, and you are to use your notes, text, or reliable websites to compile that information. Think of this as a form of studying for the quiz and later material in the course.

1. Muscovite. What bonding do you think causes the perfect cleavage to Muscovite? Turn off these bonds so that you can see "white space" for the cleavage. Show the best orientation to see cleavage of this mineral. The cleavage plane is within which axes (a-b, a-c, or b-c)? Draw and label the cleavage plane on the figure.
2. Quartz (alpha). Why is it that quartz is hard and has no cleavage? Show at least one orientation of the mineral.
3. Pyroxene (Diopside). Make the boundary range coordinates 2 or 3 (larger than just one unit cell). Turn on the polyhedra. Figure out which are the silica tetrahedra, and hide every other polyhedra. Show the best orientation to show the single-chain silicate nature of this mineral. What axis is this chain along? Circle or highlight the chains.
4. Pyroxene (Diopside). What is the approximate angle between the cleavage planes in Pyroxene? Assuming the cleavage goes through as little of the silicon-oxygen bonds as possible, turn off the other bonds, and visualize on a new slide the best orientation to see cleavage for Pyroxene. Draw and label the cleavage planes on the figure.
5. Amphibole (Hornblende). What is the approximate angle between the cleavage planes in Amphibole. Assuming the cleavage goes through as little of the silicon-oxygen bonds as possible, turn off the other bonds, and visualize on a new slide the best orientation to see cleavage for Amphibole. Draw and label the cleavage planes on the figure.
6. Plagioclase feldspar (Albite). Plagioclase has one very good cleavage and one not as good cleavage plane. Which orientations of axes are likely the two best cleavage plane orientations (a-b, a-c, or b-c) ? Show three different orientations with one axes pointing mostly up to show and annotate what you mean. Why is it that none of the cleavages are perfect?
7. Calcite. Is the bonding in Calcite ionic or covalent or both? Annotate the bonds on the figure. When calcite dissolves (such as when you put acid on it, or when acid waters attack it in nature) the bonds between which atoms are breaking during dissolution? What type of bond is this? What are the subsequent ions that go into solution?
8. Gypsum. Why do think Gypsum is so soft? Annotate on your figure. Why do think it is used in wallboard (aka sheetrock) to make the outer covering of most walls in buildings in this country?

To turn in: After you have completed the PowerPoint, convert this to a pdf with one slide per page, either with the setting as “Handout 1-per page” or “Slides.” Don’t forget your name and pledge the work. All work in this class should be pledged. After you made a pdf, then EMAIL this to me.

Please email by the beginning of lecture on Wed Jan 25.