How to get Unova Stones in Pokémon Go
Unova Stones evolve select Pokémon in Pokémon Go. Here’s how to get Unova Stones and the best uses for Unova Stones when you have one.
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/pokemon-go-guide/22545502/unova-stone-evolutions-best-use-item-list]

Unova Stones are the required evolution items for a few Pokémon from the Unova region in Pokémon Go. Similar to Sinnoh Stones, rather than adding all the niche methods for all of the niche evolution methods from the original games, we get simple items that you use with candy to evolve your Pokémon.
Our Pokémon Go guide explains how to get Unova Stones, which Pokémon need Unova Stones to evolve, and the best use for an Unova Stone when you have one.
How to get Unova Stones in Pokémon Go
Currently, the only way to get Unova Stones are through completing weekly Field Research Breakthroughs or by taking down Team Go Rocket leaders or Giovanni.
After turning in seven Field Research Tasks on different days, you can claim the stamps for a Research Breakthrough. In addition to the special Pokémon that will spawn, there is a chance to get an Unova Stone. Note that it’s not a high chance to drop, so it might be awhile before you get an Unova Stone.
Finally, Unova Stones also sometimes appear as rewards for Timed Research from events, so keep your eyes peeled for those.
What Pokémon use Unova Stones to evolve?
Currently these are the only Pokémon that uses the Unova Stone:

Chandelure and Eelektross require 100 Candy in addition to the Unova Stone to evolve. Everything else only needs 50 Candy and the Unova Stone.
More Unova Pokémon will likely need this stone to evolve as they get released.
What is the best use for an Unova Stone?
Out of the options above, Chandelure is without a doubt the strongest. The fire- and ghost-type Pokémon is quite a good ghost-type attacker, if you set it up with Hex and Shadow Ball.
Otherwise, evolving the other Pokémon is useful to flesh out your Pokédex.