Lab Work: CL Imaging Zircon Crystals

All of the mounts have been made, polished, and the zircon crystals have been imaged using cathodoluminesce (CL)! The photos below show parts of this process. 

Polishing: Similar to how we make thin sections, but all the polishing is done by hand with polishing papers that start around 30 micrometers, which is very coarse for grinding, then 15, 9, 3, and 1 micrometers. A link to a video of the polishing process is below. 

Polishing

After polishing, the grains are carbon coated before going into the SEM. There is a newer carbon coater on Westminster’s campus, but the one used for this project at Boise State University is from the 1940s (ok, probably the 70s, but still – old). The sample is loaded into the chamber at the top and sits on the little platform inside. There is a carbon rod that spits out fine carbon dust as you turn up the current. 

After the grains get a light coating of carbon, they go into the SEM (the carbon is so that they’re in conductance in the SEM). The SEM has really cool manual controls that adjust the position and the focus of the SEM electron beam. The CL detector is what makes the zircon images. The computer part of this is so that the digital images can be saved, otherwise they just appear on those little screens. CL imaging is one of the coolest parts of the process because you really get to see all the secrets that are trapped within each grain. Here’s a video as well. 

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