It’s easy to think of geology in a big picture setting but have you ever imagined geology on a microscopic scale? The Beta Rock Team definitely does. Once a section of rock is described and collected in the field it’s brought back to the lab, there samples are cleaned and polished. Cleaning and polishing helps make certain characteristics easier to spot and revealing possible unique beds that were unseen before but to gain an even more in depth understanding of the composition you must take an even closer look, that's where thin sections come in.
Depending on your sample the first step to creating a thin section will be cutting it to preserve any identifying characteristics and to about the size of a Jenga block. Once your hand sample is prepared it’s time to smooth the side you will be exposing to the microscope slide. This is one of the most important steps because if a sample is not perfectly smooth once the epoxy is applied and dried it can raise one side of the rock off of the slide causing a failure once the excess is cut off. You can sand it by hand on progressively finer medium, ranging from 200 to 800 grit.
The slide as well is often ‘frosted’ with the same grit used to smooth the sample. The glass slide you will glue the rock to must be flat in order for the rock section to end up with a constant thickness. Next a two part epoxy is mixed and applied evenly to the sample before pressing the slide onto the epoxy. Significant pressure must be applied to ensure air bubbles are forced out and a strong bond is formed. Once dry a most of the sample will be cut off using the grinding wheel leaving a thin section of sample behind. Lastly the sample must be ground down until only a single grain occupies any space at any given time.
While this process may sound simple it is very time consuming and detail oriented. There are many things that can cause a slide to fail and unfortunately you often won’t know until hours into the process. However when successfully completed you can gain a quite an understanding of your sample. Whether you use a regular microscope to identify dominant grain size or micro fossils or a petrographic microscope to determine what minerals are present in a sample thin sections can help you take a closer look.
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