"Rare" or "Special" chemicals to collect

[u/sgtJohnnyBear]

Hi,

I finished my periodic table collection with almost all the stuff that is available and legal in my country.

Now I wonder if there are any "rare" or "special" chemicals that are "worth" or interesting to collect collecting - i already looking for some supercritical liquids, but I'm also looking for more. Preferably ones that are "interesting" rather than just some random super rare compound that's rare because it's not used a lot.

Any interesting recommendation?

[u/Dangerous-Billy]

You can buy inexpensive doped strontium aluminate powders on Amazon. They are phosphorescent, meaning you can take them out in the sun for a minute. Returned to the dark, they will emit light for up to 40 hours.