If that's what the journal says, it's wrong (or you're playing a mod...kinda looks like Darkness Falls, honestly, though that would mention uranium/plutonium and titanium or tungsten or something along those lines.) Heck, the burnt forest doesn't exist any more, boulders and gravel spots have nothing to do with mining (there isn't even surface gravel outside of roads any longer), there's no "predominate ore" and stuff isn't found only near bedrock.Block damage. You couldn't one-shot certain ores or stones since A17 unless you change block damage on settings and I have never changed these parameters because I feel I'm cheating. In A20, for example, the most single-shot damage I saw was 259. (T6 steel pickaxe)
Coal. Yes, you could get coal from desert biome. That's via the ingame journal entry for mining (I don't know if they changed it in A21):
"All biomes have iron ore and a lower chance for all ores. All biomes have a predominate ore which can be found in the biome near bedrock. Special ores per biome are nitrate in snow and wasteland, lead in the forest, coal in the burnt forest, and oil shale in the desert. Boulders are typically found where ore veins exist close to the surface. Dig up a gravel spot near a boulder and you get 1 piece of the ore found below. Follow the gravel trail to the ore vein. Clay soil can be dug up almost everywhere."
So, I'm sorry, my friend, but you are wrong both cases.
If I'm remembering correctly there might have been boulders and gravel in A17 or A18 (though I might be remembering a mod) but that certainly hasn't been the case for several alphas.
Also, I regularly one-shotted stone and 2-shotted iron/lead in previous alphas. It required good tools modded properly.