The general procedure for creating thin sections has remained nearly the same since the modern version was created nearly 200 years ago.  In this module, we review two examples of modern thin section making procedures.  If you have read the history of thin section preparation (section 2.3), you should be already familiar with most of the process.

Learning Objectives

• Describe in the correct order the steps necessary to produce a standard thin section.

Prior Knowledge and Skills

• 2.2 Thin section and thick section anatomy (recommended)
• 2.3 History of thin section preparation (recommended)

Key Terms

• Frosting a slide
• Cover slip
• Chip
• Mineral stain

Guided Inquiry

Use Explaining the Thin Section Preparation (Ret. 8/19/2022) How to make a thin section. http://nationalpetrographic.com/explaining-the-thin-section-preparation-the-key-process-involved.html to answer these questions:

2.4.1 What do you do to a glass slide to “frost” it?

2.4.2 What is a rock chip? (Hint, look at part 5).

2.4.3 What should you do to the rock before you cut a slab out of it?

2.4.4 When adhering the rock to the glass slide, which should be placed on the bottom, the glass slide or the rock?

Watch these videos before answering the following questions:

2.4.5 Are the Spectrum Petrographics facilities what you imagined a thin section company would look like? Did you know that thin sections are commercially made by Spectrum Petrographics and other companies?

2.4.6 Why does Spectrum Petrographics put quartz grains in the rim of each thin section billet?

2.4.7 How does Spectrum Petrographics label the glass slides?

2.4.8 Approximately how thick is the section after it is initially cut in the cutoff saw?

Use this video to answer the next question:

2.4.9 What are the four types of stains, and what for which mineral is each stain used?

Concept Checks

Concept Check 2.4.1

Create a flowchart diagram which puts the following thin section making steps in the correct order.  In your diagram, include arrows showing the correct order of steps.  Also include some loops showing how it might be necessary to go back and re-do one or more steps if something breaks or fails.

• Cut off the chip from the slide
• Either add a cover slip, or fine polish for an electron microprobe finish
• Use epoxy to attach the glass slide to the rock chip
• Label the glass slide with the sample name
• Cut the thin section slab
• Mark the area to be cut on the rock
• Cutting the thin section chip
• Grind the rock to the correct thickness
• Grind a corner of the glass slide
• Frost the slide

Concept Check 2.4.2

What steps are different between the university lab preparation and the commercial preparation (Spectrum Petrographics)?

If you are unsure of your answers to the Concept Checks, then please re-read and re-watch the References below.  Taking notes on the readings and videos is a good way for you to summarize and remember the material.

References

AMiGEO and Spectrum Petrographics (5/19/2017) Thin Sections ft. Spectrum Petrographics: Welcome to Spectrum. https://youtu.be/_cpyazAOC80

AMiGEO and Spectrum Petrographics (6/15/2017) Thin Sections ft. Spectrum Petrographics: Behind the Scenes. https://youtu.be/Kjry4Q-qMe0

AMiGEO and Spectrum Petrographics (9/14/2017) Thin Sections ft. Spectrum Petrographics: Mineral Stains. https://youtu.be/qIGWga1ElKE

National Petrographic Service, Inc. (Ret. 8/19/2022) Explaining the Thin Section Preparation: The Key Process Involved. http://nationalpetrographic.com/explaining-the-thin-section-preparation-the-key-process-involved.html 

Spectrum Petrographics (Ret. 11/21/2018) http://www.petrography.com/

Licenses and Attributions

YouTube videos created by Spectrum Petrographics (Bonnie Hentosh and Michael DePangher), Elizabeth Johnson, Ceanna Adams, and Juhong Christie Liu.  All videos are CC-BY.

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