Suggestion: Could the shards be sand nuggets? then with the sand nuggets we craft sand ingots and make sandy tools!
gravel suggestion: maybe we could get coal and cobblestone?
dirt suggestion: gives us seeds, melon seeds and pumpkin seeds, leaves.
Some things planned is that anything being filtered will give you a random chance at getting ores / gems for example
Gravel: Rarest - Not so Rare: Diamond, redstone, lapis, gold, flint
Sand: Rarest - Not so Rare: Diamond, Saddle, feather, redstone, lapis, gold, shards
Dirt i've been thinking about but at this time No way for me to make dirt filterable. will take some time/
About the shards well i was thinking shards from sandstone but its just an idea im having at this time.
* I've tried today to make the mod need mod loader to work so i can work on my mod loader mods instead of non modloader mods but failed so i'll be most likely only making NON mod loader mods till probably June