I have grown semps in pure chicken grit, pure gravel, pure NAPA FE and even grew some in an empty pot without media. Here in this area, the three lean mixtures mentioned pick up dust, dirt, blown grass from lawn mowers, blowing leaves, etc. That means that they are not "pure" and lean for very long. The plants did well. Quick drainage and regular moisture will usually do the trick. Adjustments need to be made for cactus-like climates (lots of sun, heat and little or no rain) or dry winters without snow cover (they dry out). Otherwise, they are usually not too fussy.
