Vaseline glass beads typically contain UO2 Oxide and make very handy check sources for geiger counters.  Due to both the oxide as well as daughter decay products they produce alpha, beta, and gamma emissions. As the oxide is encapsulated in the glass, they are quite safe, in fact they have been used for jewelry for decades and can be safely handled. 

They are also fluorescent under Ultraviolet (UV) light and will glow in the dark when illuminated with a UV light source.

The regular sized beads are about 1/2 inch (12 mm) long. The large beads are about 1 inch (25 mm) long and of course produce a larger CPM reading on your geiger counter. 

Get as many as you'd like for one low shipping price, and get a great discounted price with the more you buy, up to half off!