Calcium - known to every schoolkid as some vaguely healthy substance in milk and cheese - is an element whose true nature is much less well known to most people. The metal simply cannot exist in nature uncombined with other elements because it is too reactive; that is, too willing to pair its atoms with other atoms to form molecules.

While in free form it is unknown to so many its molecules sure aren't: CaCO3 gives us both chalk and marble while the slightly different CaSO4 is much better known as the sheet rock that lines most American homes. Your very bones are a brew of calcium phosphates.

Even though you get it from drinking milk and yogurt, people shouldn't be surprised to learn that calcium is a metal. After all, reading through the ingredients list on a cereal box there's iron and magnesium and others too. But the thing is that calcium isn't something most are familiar with as an object.

And yet, it really is a metal. On the moon it would make for a perfect metal to make, I don't know, a cell tower or something. It's very light and plentiful. Why the moon? Well, because there's no atmosphere or water there that could come in contact with our imaginary calcium tower. Either of those touch it and the calcium instantly sizzles and corrodes.

No worries though. Our sample here is stored in argon to keep that delicate luster alive for all eternity. Well, as "eternal" as the cube don't get broke, that is! ;-)

This offering is for one ampoule containing a piece of 99.99% pure calcium metal embedded in a 50x50mm block of crystal clear Lucite acrylic. Hand cast in the USA.