  Antique lantern mantle.
Lantern mantles, which glow very brightly when heated by an oil flame in a camping lantern, used to be made with thorium oxide as the primary incandescent material. Thorium was used right up the 1990's, but has now be replaced with various other rare earth oxides.
These were claimed by the seller to date from the early 1900's, and considering how fragile they are, I can believe it. Two of the three I bought were basically smashed to crumbs (radioactive crumbs) on arrival, the third was in perfect condition for photography, but sadly lost a chuck due to an accidental tap on being replaced in its container. Sad, but it would almost certainly have crumbled on its own soon anyway, the material is basically turning to dust.
This is a picture of the nice cardboard can it came in:
Source: eBay seller boco007
Contributor: Theodore Gray
Acquired: 11 March, 2007
Text Updated: 12 March, 2007
Price: $10
Size: 2"
Purity: <20%
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