Granite has a medium pitch voice, and his tone is usually low, blank, and calm. He doesn't have much emotion in his voice and is quiet enough that it could be seen as somewhat annoying. Think of James from Telltale's The Walking Dead Season 4, but slightly older. He's more a young adult than a teenager. 

https://youtube.com/clip/UgkxTq6ziM4Y7tRBVHcNE-wcqy_rlPuAzzWC

Granite is outwardly quiet and a nonchalant dragon. He can come off as introverted, dark, silent, and even cold at first glance, and keeps these attributes towards strangers. His temper tends to show to those he knows more. He's susceptible to anger and can become peppy and frightful upon danger. He's creative and friendly and has a high love for those he loves. But in the end, he's quiet to mostly everyone.

The casted actor must be able to do a younger version of the voice.