Originally Posted by
DennisBarberShop
The thing about naturals is this....the rocks grow in layers from sediment on the ground at first, then as layers piled up over years-decades-centuries-millenniums....kinda similar to rings in a tree, they build up weight applying pressure and eventually changing the structure, can effect grit, shape of particles, etc. Considering how much the sediment could change over time, each layer can vary in grit so an inch of rock can vary in composition from top to bottom by a lot....or a little or none at all depending on the conditions the stones went through. If you look at a lot of thuringian stones for example, or deal with many of them youll start noticing a lot of them with one side of the hone a lot darker than the other with a distinct line in them where it transitions. Or you can drive through a cut in a hill where your roads pass through and see the layers, thick rock layer followed by looser rock materials with huge variations in color as well.
Best way I know to explain. Hope this helps