This
section draws substantially from the techniques section of the Sandstone
Tutorial. Milliken, Choh, & McBride, 2007, AAPG Discovery Series, No. 10.
What works for sandstones tends to be useful for carbonates, too!
Today, students of petrology must be familiar with a wide range of petrographic methods. Each method offers particular strengths for extracting information from rocks. Limiting oneself to but a single method yields a very incomplete "picture" of a rock's mineralogy, texture, and history.
"I wouldn't have seen it, if I hadn't believed it!" -Marshall McLuhan
When looking at images from any one method, experienced petrographers always begin to conjure up ideas of what might be seen by using another method. Would the apparently simple crystal seen in plane-polarized light show zoning in back-scattered electron imaging? Would that plane of fluid inclusions within in a grain mark the center of a mineral-filled fracture as seen in cathodoluminescence? Would SEM reveal that echinoderm fragment to be riddled with a network of micropores? Awareness of the full array of petrographic methods opens avenues for imaginative questioning about what you see in rocks and encourages you to make the most of the observational possibilities at hand. For example, if you're aware that cathodoluminescence and back-scattered electron imaging often reveal evidence of zoning in crystals, then you're more likely to stretch your powers of observation to detect whatever subtle clues for this may exist in transmitted light. Knowing the flexible options that exist for answering questions frees you to be more adventuresome in devising questions.
The sections listed above provide basic information on the petrographic methods that are applied widely to carbonate rocks. The beginning student should seek to learn how each method works and the nature of the data obtained from each, and learn to recognize each type of image on sight. The more advanced student should become experienced with the typical appearance of common rock components in each method.
As mentioned in the introductory materials, this tutorial is devoted to a specialized examination of carbonate petrology. Students who wish to become accomplished with the skills for describing and interpreting what they see in carbonates must be prepared with a solid grounding in mineralogy, crystallography, crystal optics, and a wide variety of analytical methods (especially statistics).