Blue Clay above Gravel

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Didn't know whether to post this here or in Rocks & Minerals, decided here since there is more activity here.

My parents had some testing done for possible sand & gravel operation on the family farm some 20+ years ago by a company from Minnesota, we're in Western North Carolina. When the company finished testing they gave our family a description of two fields near creek where they tested and results from different test holes. In one of the fields which is 5 acres I notice that most of the test holes indicate gravel or sand/gravel over blue clay. However in a couple of places it shows gravel under the blue clay, for example: 5' dirt, 2' blue clay, & 2' gravel. Is there any significance to this related to gold and/or gemstones ? Company is no longer in business so can't talk to them.

Some of you are probably geologists or have geological experience, would appreciate your views & thoughts.

PS Have a pair of 10' post hole diggers on order so maybe I can verify if it there is need to and if that don't work can always get a trackhoe, these test hole are not that close to the current creek.