We just learned about the type of element Calcium.
Corundum is a type of gem stone that can be many different colors, red, yellow, pink-orange, green or blue.
If the corundum is red, it is called a ruby. Otherwise it is called a sapphire.
Corundum is very hard and rough, is sometimes used on sandpaper or on large cutting machines.
It is made up mostly of the chemical elements of aluminum and oxygen combined together.
(from: wikipedia - corundum)
Kid Facts - Blast from the past: Diode
