This substance throbs with fiery energy and it is more than eager to release that energy at the slightest bump. It may be unstable, but it would probably make a good source of fuel. It is probably not a good idea to throw it against a solid surface unless you enjoy explosions.
Alumentum is a very volatile substance. When held in your hand, you can throw it and it will travel in a small arc like a potion and explode upon impact against any mob or block.
It can also be used as fuel and will smelt 32 items in the furnace, burning for 25% longer than than the 3 coal used in it's crafting.