Thursday, May 20, 2010

Electron Microscope Image of Fluorite

Image of a fluorite crystal mined from Rosclaire, Illinois in the fluorspar district.  It is the state mineral of Illinois which was at one time the largest producer of fluorite in the United States.  The mineral is composed of calcium fluoride and its primary industrial use is in steel making (flux to remove impurities).  Fluorite is also found in Kentucky which has the Ben E. Clement mineral museum dedicated to its mining in Marion, Kentucky.

What does the surface of fluorite look like?  We need a microscope to magnify it.  Using an optical microscope at 40x magnification, one can see something like in the picture below.  Definitely there is room for improvement so one can use a scanning electron microscope (SEM) to see a much more precise view of its surface.

Luckily, a company in Delmont, Pennsylvania called ASPEX Corporation has a promotion where they will scan objects for free.  So sending them a small crystal of fluorite and a filled out form, they sent results back in about 10 weeks (it is popular and a lot of people are sending them material to scan!).

The analysis and report was done by Binyam using the PSEM eXplorer (shown in the image below) to analyze the fluorite crystal.  A manual SEM and EDX Analysis was done using Backscatter electron detection (BSED) to collect images under variable pressure conditions (0.15 Torr) and 20 KeV.

The results are shown below with 200 um and 100 um scales on the images.  This crystal surface was formed over 100 million years ago when fluorine rich water from the earth's depths made contact with calcium rich limestone closer to the surface. 

In the images shown, I assume most of the coarse surface detail is grit from mud and sand the crystal was found in.  An interesting experiment would be to clean the crystal in an ultrasonic bath in different time increments to see if this material disappeared or not.

ASPEX also scanned a fossil of 400 million year worm tube for me, see that report at this web link. See more samples of every day items at ASPEX Corporation's website.

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