Limestone contains calcium carbonate, a base. Therefore it will dissolve when acidic rainwater flows through it, creating caves. Sandstone contains many pores that are of various sizes that can filter out groundwater pollutants, but they are well connected so that water will flow through them at a useable rate. It does not contain high levels of harmful minerals, and does not readily weather. Therefore, it is the rock in KY most likely to produce a drinking well with clean, safe water.
Shale contains clay and is in small, thin layers.
It easily breaks down during rain events to form regolith as seen in roadcuts on the side of the road. However, most of the minerals in shale are not readily reactive with acidic rain or oxygen, so it does not readily weather through chemical means. Sandstone is made of quartz, a chemically nonreactive mineral that does not readily undergo chemical weathering. Sandstone is more durable than shale, but when weathering does occur, it is primarily from physical weathering processes. Limestone is created by the body parts of sea creatures.