Enjoying Rocks Under the Microscope

A "thin section" is made by gluing a rock chip to a glass slide and then grinding the rock to a thickness less than paper.  Under ordinary light, the result is rather colorless, but when the slide is placed between pieces of polarizing film, the interference of light rays produces results which are both spectacular and diagnostic for specific minerals.

The purpose of this section is to invite the lay person or high school student into the world of rocks under the polarizing light microscope (PLM).  Several images of a  metamorphic rock known as "kyanite-muscovite-biotite-garnet schist" can be viewed in the Photomicrograph Gallery.

This page will guide you to the minerals you see in the gallery and the properties by which they are identified.  It concludes with links to other sites that will continue your introduction to rocks under the microscope.

Minerals and their properties

The minerals seen in the gallery slides include the following: These minerals are distinguished by the following properties:
Additional properties are described in some of the references below.

Links to Other Sites

Humboldt State U. Petrography tutorial
A systematic survey of minerals making up igneous, metamorphic, and sedimentary rocks.
Minerals under the Microscope
Very nice discussion and illustrations of the properties of minerals as seen under the microscope.  The down side: All the aspects are placed on a single page which takes many minutes to receive (from Australia to the U.S.) even on a fast internet connection.
The Virtual Microscope
Access to software and QuickTime files that allow you to see how a thin section changes its appearance as it is rotated on the microscope stage.  Instructive, but you must download software and will need a fast internet connection.
Kevin Smith thesis pictures
Pretty pictures from a thesis on high-grade metamorphic rocks, part of an individual's web pages.
Igneous Rocks - Duke U.
A few typical igneous rocks both in hand specimen and thin section - from a college course.