Pokémon GO dataminers have discovered a new item called the Sinnoh Stone. This special item will be required to make certain Sinnoh Pokémon evolve. Its official description is as follows:
A special stone originally found in the Sinnoh region that can make certain species of Pokémon evolve. It is very tough and has a beautiful sheen.
Source: Reddit.com/TheSilphRoad
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