Crystal and Glass Formation from a Melt and a Glimpse into Archaeometallurgy Through the Eyes of a Binary Eutectic Phase Diagram
University of Dayton
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This lab gives students the opportunity to investigate crystallization processes and textures. Students experiment with a crystalline wax, studying how/where the crystals form, how to get crystal-free material, and how different cooling rates affect crystal size and distribution.
This exercise is designed for a sophomore or junior level required course in petrology.
Skills and concepts that students must have mastered
Students should have a basic understanding of how to read a phase diagram.
How the activity is situated in the course
This is a 3-part stand-alone activity.
Content/concepts goals for this activity
I have discovered that students seem to struggle with the idea of quenching and how it serves a snapshot of a phase diagram at a set temperature and composition. This 3 part lab walks students through self-designed experiments, glass in real samples, and then to a binary eutectic phase diagram exercise.
Part three of the lab brings to light the idea that petrologic concepts extend out of the world of geology. Part 3 is an exercise where students address archaeometallurgical questions based upon information from a phase diagram.
Higher order thinking skills goals for this activity
This activity involves data analysis.
Other skills goals for this activity
Description of the activity/assignment
This lab gives students the opportunity to investigate crystallization processes and textures. Students experiment with a crystalline wax, studying how/where the crystals form, how to get crystal-free material, and how different cooling rates affect crystal size and distribution. Students can even create their own pillow lavas and flow/cooling textures. The experiments also provide an opportunity to clarify the idea of quenching for students. Once students understand quenching, they have an easier time completing the included exercise which involves looking a binary eutectic phase diagram and the modal abundances of glass and crystals in a real sample. The phase diagram and modal information are used to determine a melting/quenching history and composition for a historical sample of metallurgical slag.
Determining whether students have met the goals
Students have met the goals of this assignment if they answer the assigned questions thoroughly and accurately.
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