Keith Putirka

California State University, Fresno

Mineralogy (at CSU Fresno, EES 12). This is usually the first course "in the major" for our students at CSU Fresno. Prerequisites are Physical Geology, and CHEM 1A (a standard first semester course in Chemistry) or CHEM 1A "concurrently."

Before giving this assignment, I usually have introduced the following:

1) The Fo-Fa binary phase diagram. I will give students a bulk composition, and then ask them to trace the history of melting or crystallization.
2) The concept of a "phase" and of mineral components.
3) An introduction to Excel, showing students how to enter an equation, and use the fill-down commands
4) An introduction to the equilibrium constant (this is review from CHEM1A, but students usually appreciate the repetition, and often state they feel they learn more Chemistry from these exercises than they do in their CHEM course...)

This is a stand-alone exercise, usually assigned as homework, after an in-class demonstration of the calculation of mineral components, and a review of binary solid solution phase diagrams (which I introduce very early on in the class).

This homework assignment allows students to practice calculating mineral components, providing tests for equilibrium, and coding into Excel a simple thermometer.

The higher order aspects are the tests of equilibrium – students must decide which of the mineral-liquid (whole rock) pairs yield temperatures that are viable, and which calculated values for T should be discarded. They must think through the limits to which such tests can be applied, and why some data, though from a published source, might still not yield useful information (and they must understand that what is "useful" depends upon the question(s) being asked).

I ask student to do this assignment using Excel, which takes a little bit of know-how in regarding to coding equations and using the "fill-down" command. I often give one or two lectures in our department computer lab, so the students can practice working with Excel, with my help. This assignment, though, can be done "by hand."

This assignment is ostensibly about geothermometry, but is also part of a sequence of assignments where students learn about mineral components – what they represent (in regards to solid solution phenomena especially), and how they calculated. I begin with olivine because its components are simple, and reasonably good thermometers do not require long equations. I also use this assignment to teach about binary solid solutions and phase diagrams, though the interpretations of such are based within other assignments.

This is part of a sequence of assignments where students learn about mineral components – what they represent (in regards to solid solution phenomena especially), and how they calculated. Though students will not use a binary solid solution diagram per se, I use this HW assignment to re-emphasize such concepts. This assignment also allows students to begin tests of equilibrium, so they must understand the concept and use of an equilibrium constant.

I check to see that the students correctly calculate temperatures for all mineral-whole rock pairs, and can identify which temperatures are possibly useful, and which are meaningless.

My web site (http://www.csufresno.edu/geology/Faculty&Staff/Putirka/Keith_Putirka.html) has a spreadsheet for olivine-liquid calculatins, but I do not mention this in class, as I like to see students attempt the calculations on their own (which is why I do not used a published thermometer, even though their are other thermometers which are more accurate). But the web site could be useful to provide students with a self check, after the assignment as been completed.