Water well drillers here use bentonite to help solidify the ground where they are drilling (some areas are VERY sandy) so the hole doesn't collapse as they are drilling.

Good idea on the alternative sources!!

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).