Link provided by Kent.
Prairie Magazine reported back in November, 2012:
The North Dakota State Geological Survey recently completed a mapping
project to investigate the potential for clay deposits located in the
southwestern part of the state to be mined for the production of ceramic
beads used as a proppant in hydraulic fracturing activities. Ceramic
proppant is one of two types of proppants currently used in hydraulic
fracturing activities in the Bakken region.
State geologist Ed
Murphy collected approximately 200 rock samples from 61 sites in two
kaolinite-rich geologic formations stretching across an area that
includes the cities of Dickinson and Bowman. Collected samples were then
analyzed for aluminum oxide content, which is a desired component for
proppant material. According to Murphy, clay containing at least 20
percent alumina has the potential for use as a proppant. A small number
of initial samples displayed an aluminum oxide content ranging from 26
to 38 percent. The larger sample pool showed to contain lower
percentages of aluminum oxide, but Murphy believes the content could
still be high enough to be useful. The state’s mapping project will
serve to assist interested parties in further exploring the potential
resource. “We’ve laid the groundwork for a company to come in and do a
more detailed investigation,” he says. “Ultimately, they will need to do
some small-scale mining and run that clay back into their plants” to
see if it works.
It's possible this has been posted before (I don't remember) but it's relevant, again, in light of
Minnesota's plan to consider a moratorium on mining fracking sand.
