The Tallonian homeworld was an inhabited planet and the homeworld of the Tallonians.

Tallonian crystals originated from the Tallonian homeworld and were considered contraband anywhere but on the planet. A special type of equipment called a type 4 Tallonian microscanner was used to determine the purity of the crystals. (DS9: "Hippocratic Oath")

This planet was only mentioned in dialogue.
A Tallonian crystal prop was sold of in the It's A Wrap! sale and auction on eBay. [1]