Radium in pure form is a radioactive metal with a slight blue glow, but it is very very rare to see it in pure metal form, or in any amount bigger than "Tiny".
Radium has the atomic name "Ra", atomic number 88, and the most common isotope is Ra-226. It's at the bottom of the Alkali-Earth metals, and is chemically similar to Barium.
It was discovered in 1898, when radioactivity wasn't very well known, by Marie Curie, found mixed in with a Uranium ore known as Pitchblende, once the Uranium was removed from this ore, the by-products, which where mostly Barium with traces of Radium, where still radioactive.
In the 1930s or so, radioactivity was considered a big deal, Radium was a popular word, and was quite commonly discussed by the general public. It was used in countless useless applications because it was thought to be healthy at the time, at one point you could buy Radium drinking water, Radium hand lotion, and a number of other bogus products.. Some of which really did contain Radium.
One actually useful application of Radium was discovered in the fact that the radioactivity of Radium(And Radium compounds, such as Radium Chloride) would react with the chemical compound Zinc Sulfide, and produce visible light, similar to "glow in the dark" items, but would last 20 some years without recharging in sunlight.
A company known as the the United States Radium Company(among other companies in various countries) manufactured a paint containing these chemicals, and it was used on wrist watches, switches, dials, anything that needed to be signified in the dark. Many military meters and gauges used Radium paint. However, in the 1960s, girls employed to hand-paint these items began to contract bone cancer from the exposure and light consumption of Radium (They used their mouths to re-shape their paint brushes), which lead to a lawsuit against the company, and a world-wide end to Radium paints.
I, however, was lucky enough to buy a broken watch from the 1920-40s off of Ebay containing this very paint. The risks of Radium to the wearers of these watches is much less than to the painters, and many where worn 24 hours a day with no side effects, but still, I won't be wearing mine.
I'm not sure how old this watch is or where it came from, but it is swiss made, and I think before 1960. On the left is the glow AFTER being charged with ultraviolet light, the Zinc-Sulfide in the Radium paint won't glow from radiation after about 20 years because it breaks up crystals vital for the glow, and it doesn't glow for very long under ultraviolet, just long enough to show what it might've looked like years ago when it was still good.
That's my post on Radium, thanks for reading!
~Ben