Undergroundwater can be rather diversified. It can travel in streams small and large .. seep to the surface or stay under ground .. be heated by a magma and carry raw silica out of volcanic ash and deposit it when it flows out at the surface and cools .. travel cold and pick up very little.
The rock and strata it travels through can be sedimentary, metamorphic or igneous (volcanic). Of these three types .. sedimentary is the best for having soluble minerals or diatomaceous deposits.
The number one item found when cleaning out the screens in portable toilets are "___ a day" brand vitamins with readable labels still on them. Gel cap powder is the best idea in vitamins for some .. unless you like bullets.
At a deer lick .. you have the chance to collect dirt that is rich in "mineral saturated" "water born deposits" or just a rich "spot" in a strata of earth.
Some underground water in the Three Creek area of Idaho is so rich in fluoride .. it kills cows.
To this scenario are weeds and plants that tend to concentrate certain minerals if they are available to the root system. These minerals are soluble if soaked in a vat for a spell and can be harvested at the atomic nutritional level.
Liquid Life .. Oklahoma ..started out doing just this.
Video of all the PDC and ATC (~177 hours) - HD instant view