While its pretty normal to associate milk with calcium, in its pure elemental form, calcium is a shiny silver grey metal! The calcium found in milk is the ionic form of calcium, having shed two electrons to form a +2 charged cation. What I think is really cool though is what you can do with just a bit of elemental calcium and some water. Calcium reacts pretty violently with water, forming a white solid called calcium hydroxide and giving off lots of flammable bubbles of hydrogen gas. If you filter off the solid calcium hydroxide and heat it, it decomposes into calcium oxide, also known as lime. And this stuff acts really unexpectedly when you heat it really hot. It undergoes a process called candoluminescence, where additional chemical processes lead to emission of light much greater than during incandescence. The effect is so bright that we used to use this process to illuminate actors on theatre stages! Chunks of calcium oxide were heated with hydrogen torches resulting in a brilli...