2.1 Overview: Thin Sections and Thick Sections
Elizabeth Johnson; Juhong Christie Liu; and Mark Peale
Petrographic thin sections, or thin slices of polished rock attached to a glass slide, are used for a variety of analyses by geoscientists. The same basic steps have been used since the 1800’s to create thin sections, but the technology and materials have changed.
Some people love making thin sections because the process can be meditative, though not always quiet if you are using a rock saw! Others can find the process frustrating, especially the last step which requires patience to slowly approach the final required rock thickness without destroying the sample.
If you are a student, it is better to focus on process rather than outcome. In other words, it is better to think, “How do I do this step well? Let’s try again!” rather than “I need to make a perfect thin section by Friday!”
This, of course, is not true for companies which produce thin sections for customers. Thin section companies must meet deadlines and quality control standards. The materials presented in this module include videos and footage from university thin section laboratories, as well as videos from Spectrum Petrographics, a commercial thin section company in Vancouver, Washington. We provide a range of footage to show how facilities and techniques vary among teaching and commercial laboratories.
At the end of this module, students should be able to:
- Describe the parts of a standard thin section.
- Describe the differences between a standard petrographic thin section, a thin section prepared for electron or ion microbeam analyses, and a thick section.
- Summarize the history of thin section preparation in the geosciences.
- Describe in the correct order the steps necessary to produce a standard thin section.
- Explain the purpose and function of each piece of equipment used to prepare thin sections.
- Explain how to use thickness standards to determine when a thin section is at the correct thickness.