Public Lab Research note

Frac Sand mining- polar light microscopy?

by mathew | April 22, 2014 01:02 22 Apr 01:02 | #10341 | #10341

This image is from Wisconsin Watch

With the increase in fracking comes a demand for sand used to keep hydraulic fractures open. Not just any sand will do-- it has to have the right particulate size, and therefore is best sourced by crushing and sorting sandstone. To read a summary of silica monitoring, see the wiki page I just made.

Particle Monitoring for Silica

Several open source projects are currently pursuing particulate monitoring, the Dustduino, Speck, and perhaps even the Open Lux Board

As I pointed out in the Silica wiki page, most dust monitoring has traditionally occurred in occupational environments where the total dust exposure was assumed to be largely of the particles of concern. In a fenceline community, dust could be from any number of sources, so particulate characterization becomes key. Gross particulate measurements such as PM10(For an overview of particle monitoring terms, see the wiki) require correlation with Wind direction, local soil conditions, and a variety of factors. These correlations will require some sort of identification of silica.

Identifying Silica

Polar Light Microscopy


Granite under polarized light, Thomas Bresson via wikimedia commons

Scanning dust that has settled on a sticky pad or in a filter has been a method of dust monitoring. with a high-quality scanner or microscope and polarized light microscopy, could silica be picked out? the silica particles above are the most colorful. Other methods that are traditionally used involve X-rays.

There might also be an infrared method of analysis, detailed in this paper. I have to get it and read it: Pandurangi, R. S.; Seehra, M. S.; Razzaboni, B. L.; Bolsaitis, P. (1990) Surface and bulk infrared modes of crystalline and amorphous silica particles: a study of the relation of surface structure to cytotoxicity of respirable silica. Environ. Health Perspect. 86: 327-336.


We could use smartphone or laptop screens for polarized light, or steal 3d glasses from movie theaters. I guess polarized light isn't in short supply.

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I got some big (4"x8") sheets from american science and surplus. I was going to see what happens when I put some silica dust down on a flatbed with one of those underneath. 3D glasses are cylindrically polarized and might not work right. we need linear polarization (which, incidentally, is the cheapest).

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At an optics conference, a while back Edmund Optics were giving away a lot of credit card sized polarizers, worthwhile reaching out and seeing if they can donate a bunch.

A couple of decent option would also be: and if circular polarization is interesting (this is what most camera polarizer filters use):

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