You cannot splice this item. LAVA CUBE is in damage category. You get experiance points for breaking LAVA CUBE. You do not need mods to break these. By default you should get at least 1 seed back. Gemratio of LAVA CUBE is a mystery. Maybe you can check the wiki for <a href="https://growtopia.fandom.com/wiki/Lava_Cube">lava cube</a> Will you get enough blocks to build something? You just have to find out yourself.