Uranium glass

After uranium was discovered, one of its early uses was in the coloring of glassware. The classic and virtually unique colors

"ranged from turquoise to green to yellow to topaz to amber within which there is almost a continuum gradually changing shades. Perhaps the most popular of these amongst collectors is what has become known as “vaseline” glass. It is greenish yellow with a slightly oily appearance and closely resembles the well known petroleum product."

That's interesting, but the next part is even better. Uranium glass fluoresces under ultraviolet light. And apparently (I didn't know this) such fluorescence could be seen even without a black light, using the light of the setting sun:

Although gas lighting was starting to make an impact a lot of properties still relied upon oil and candles. These would not be lit until the last moment when the twilight finally gave way to darkness. As the sun sets the first colour in the spectrum to go is red, the last is violet and with it the neighbouring ultra-violet. Thus as darkness falls the ultra-violet component of the spectrum predominates and uranium bearing glass starts to glow. It must have been an attractive sight in those homes of long ago.

Very cool. You learn something every day.

There's also information, photos, and more links at Wiki, but the photos and text above come from the very interesting 20th Century Glass website.