Gravel and Sand ore shouldn't be pulverize-able. You must hammer them.
tl;dr version
Automation (when you get there) = Profits.
Hammering = Waste of Time (the most important resource)
You don't need to hammer them when you have automation. . . Either by having Cyclic Assemblers or MAC craft them and smelt them in the smelting option of your liking. If you go really big and use multiple TiC Smelteries you never need to do anything more than dump the Broken Ore (from sifting gravel) or the Pulverized Ore Dust (from sifting dust) right into the Smelteries. You will be making so much during automation, while you are doing other tasks that the extra you could get from hammering won't even be missed.
(edited for cell phone derp)