We just learned about the type of rock Corundum.
Another chemical element is Potassium, called "K" for short (from the latin word kalium) on the Periodic Table.
Potassium is a type of metal that is very soft, and can easily be cut with a knife.
If you put potassium in a glass of water, it will make a big explosion!
When the potassium is in the water, it mixes up with hydrogen and oxygen.
As it is mixing together, the chemicals let off a lot of heat.
With all that heat, some of the hydrogen gas lights on fire, and then it goes kaboom!
We have potassium in our bodies, but it's not the same as the potassium metal that explodes.
It's sort of like what's left from the mixed up potassium after the big explosion, so it's safe.
(from: wikipedia - potassium)
Kid Facts - Blast from the past: Photons
