Now that you are familiar with how to use a petrographic microscope and some of the optical characteristics that can be observed for minerals, it is possible to identify minerals under the polarizing light microscope (or at least to eliminate some possibilities).

This section is intended for use as a reference for students who have completed the earlier sections of this chapter.   Sources to locate optical data as well as images of igneous and metamorphic minerals are compiled below in alphabetical order by reference name.

Please note that this is intentionally NOT a comprehensive table of data for each mineral. In the next section of this chapter (2.10) there is a student synthesis assignment in which students compile their own tables and criteria to distinguish commonly-occurring rock-forming minerals.

Resources: Optical Properties

John Fathfull (ret. 1/12/2020) Identification Tables for Common Minerals in Thin Section. http://funnel.sfsu.edu/courses/geol426/Handouts/mintable.pdf

NOVA Mineralogy (ret. 2/16/2021) Minerals. https://blogs.nvcc.edu/mineralogy/minerals/ 

Smith College Geoscience Students (ret. 1/12/2020) Petrographic Data Files. http://www.science.smith.edu/geosciences/petrology/petrography/mineral_list.html

Webmineral.com (ret. 1/12/2020) A to Z listing of minerals . http://webmineral.com/Alphabetical_Listing.shtml#.XhtMwchKhGM

Resources: Minerals in Thin Section

Atlas of Metamorphic Minerals (ret. 1/12/2020) http://www.earth.ox.ac.uk/~oesis/atlas/metmins/index.html

Hollocher, Kurt (ret. 1/12/2020) Igneous Minerals in Thin Section: https://minerva.union.edu/hollochk/c_petrology/ig_minerals.html

Hollocher, Kurt (ret. 1/12/2020) Metamorphic Minerals in Thin Section: https://minerva.union.edu/hollochk/c_petrology/met_minerals.html

Mazdab, Frank K. (ret. 1/12/2020) thin section scans. https://www.rockptx.com/thin-section-scans/

NOVA Mineralogy (ret. 2/16/2021) Minerals. https://blogs.nvcc.edu/mineralogy/minerals/ 

rockPTX (ret. 1/12/2020) Playlist of mineral videos in thin section (ppl, xpl): https://www.youtube.com/channel/UClRPHZ4xYNB6BCQ3zaIv9Pw/playlists

Siddall, R., 2014, Minerals Menu: a catalog of minerals & textures in thin section. http://www.ucl.ac.uk/~ucfbrxs/PLM/PLMhome.html

Virtual Microscope (ret. 7/6/2020): Contains collections of rocks and meteorites in thin section. https://virtualmicroscope.org/

Optical and Crystallographic Axes Diagrams

The diagrams below show the geometric relationships between principle optical axes and crystallographic axes for some common biaxial rock-forming minerals.  In these diagrams, OA = optic axis; X, Y, and Z are principal optic axes; a, b, and c are crystallographic axes.  Crystal faces are labelled with Miller Indices (e.g. 001, 110, etc.).

Feldspar Group

Talc

Mica Group

Chlorite Group

Amphibole Group

Pyroxene Group

Epidote Group

Olivine Group

Aluminosilicates

References

Optical and crystallographic axes data for figures are taken from:

Deer, W.A., Howie, R.A., and Zussman, J. (1992) An Introduction to the Rock-Forming Minerals (2nd Edition).  Prentice Hall. 712 p.

Nesse, W.D. (1991) Introduction to Optical Mineralogy. Oxford University Press, 335 p.

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