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
caoutchouc
lplolol
freezer
2x tube
steam and air.
earth + fern
Swamp and sand
Chickens and Grain