Pokmon Go finally has begun to add Pokmon from the Unova region. For some of the evolved forms of this regions Pokmon, players will need Unova Stones, a rare evolution item, similar to the Sinnoh Stone that released before.

Unova Stones work like other evolution items. A handful of evolutions will require them, in addition to candy, to evolve specific mons.

Currently, the only way to get Unova Stones are through completing weekly Field Research Breakthroughs. After turning in seven Field Research Tasks on different days, you can claim the stamps for a Research Breakthrough. In addition to the special Pokmon that will spawn, there is a chance to get an Unova Stone.

Note that its not a high chance to drop, so it might be awhile before you get an Unova Stone.

Currently these are the only Pokmon that uses the Unova Stone:

The three monkeys, Pansear, Pansage, and Panpour, all need 50 candy, in addition to the Unova Stone, to evolve. Lampent needs 100 candy and Sinnoh Stone to evolve.

More Unova Pokmon will likely need this stone to evolve as they get released.

Out of the four options above, Chandelure is the strongest. The fire- and ghost-type Pokmon is quite a good ghost-type attacker, and some analysis noting that its the second best ghost-type attacker in the game, only falling to Origin Forme Giratina.

Go here to read the rest:

Pokmon Go: Where to find Unova Stones and evolve fifth-gen Pokmon - Polygon