In Alchemy Classic, you can create limestone by combining the elements of stone and fire. First, select stone from your inventory and then combine it with fire. This will result in limestone being produced.
You cant make alchemy classic, its a game! Though you can download it and play it!
Shell+stone=limestone
in alchemy classic its 2 bacteria but it might be different in the original (assuming your playing alchemy classic)
shells + stone
lplolol
caoutchouc
freezer
Air + Fire
Metal earth
Earth and flowers
Air+air
Earth + Grass