Verified answer

1) Gravel

2) Silty Sand *

3) Fractured Basalt *

4) Sandstone

5) Clay

6) Shale

* Take note, depending on the amount of fracturing, it could be less than sandstone.

Check some USGS publications if you want to know...something on Basic Ground-Water Hydrology should work.

Gravel, Sandstone, Silty Sand, Unfractured Basalt, Clay, Shale

In addition to that, Clay and Shale will often have more hydraulic conductivity parallel to the bedding plane rather then vertical to the bedding plane. Also, fracturing plays a large part in hydraulic conductivity but assuming fracturing to be non-existent, the list is in the correct order.

gravel, sandstone, siltysand, basalt, clay, shale

based on porosity and hydrostatics