Optical mineralogy reference tutorials and unknowns on YouTube

Monday 11:15-11:45am PT / 12:15-12:45pm MT / 1:15-1:45pm CT / 2:15-2:45pm ET Online
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Matt Kohn, Boise State University


Examples of both types of videos.


These videos are not directly an activity, but rather serve as a publicly-available foundation for upper level undergraduate lab instruction in optical mineralogy and igneous and metamorphic petrology. A set of ~50 reference tutorials covers most major minerals (quartz, plagioclase, garnet, etc.) plus some key topics in optical mineralogy (pleochroism, cleavage, etc.). These tutorials have voice-over explanations and options for comments. Another ~200 videos show "unknowns" – rocks that have readily identifiable minerals, but without explanation or option for comments. A google doc answer key is available to instructors for the unknowns, along with a list of topics that I use the rocks to teach about (pleochroism, relief, textures etc.). The videos serve as a reference point summarizing key mineral characteristics, and as an on-line option for viewing minerals in thin section.


The target audience is for undergraduate students in optical mineralogy or petrology. They should have a general working knowledge of petrographic microscopes. At present, lots of technical terms are used. I use the reference videos to help students master mineral identification. I use the unknowns videos for lab assignments and for tests/quizzes.

Why It Works

Sometimes students just want content, and there's not much on the web with this level of detail. Also, these rocks have been assembled over ~20 years, and are particularly effective for teaching about minerals and textures. There are web resources for optical characteristics of minerals (e.g., Frank Mazdab's https://www.rockptx.com/video-atlas-of-minerals-in-thin-section/), and for looking at rocks in plane and cross-polars and manipulating sections (e.g., virtualmicroscope.org) - See Jennifer Cuthbertson's Share-a-Thon. But they don't have the range of mineral assemblages and textures covered in the current set of videos.