A new stone has made its way in Pokemon GO, the Unova stone, it allows you to evolve generation 5 of Pokemon. It cannot be used to evolve Pokemon from previous generations, but it will be used to complete the unique evolution stages of Generation 5.
Chrales revealed the stone on Twitter through a leak. Its description indicates that it can "evolve certain species of Pokemon".
How to obtain the Unova Stone is currently unknown. Although if it looks like the Sinnoh stone, then it is likely that the stone will be received by the same means as the Sinnoh stone. By defeating other trainers in PVP battles or by collecting the Day 7 reward on the field.
Which Pokemon will need the Unova Stone
There is a wide range of Pokémon in the Fifth Generation that feature special evolutionary conditions such as requiring a Twilight Stone or reaching a certain level of Friendship. The Unova Stone from Pokemon GO could potentially replace them.
The following Pokémon all have a unique condition to evolve; they are all potentials for the Unova stone:
Baldore
He evolves into Gigalith by being traded
woobat
He evolves in Swoobat having a friendship level
Gurdurr
This Pokémon evolves into Conkledurr through trading
Swadloon
Needs a high level of friendship to become a Leavanny
Minccino
Need a shiny stone to evolve into Cinccino
Karrablast
He was traded for Shelmet to become Escavalier
Lampent
Need a stone at dusk to become Chandalure
Shelmet
Evolves in Accelgor after being traded for a Karrablast