Granite is a Telepath who works with the Black Swan. He is also known as Sir Tiergan and is a member of The Collective. As mentioned in the book Neverseen, he consumed a chalky powder called Indurite. It causes his body to crystallize and harden, making him look like a talking statue which is most likely why he is called Granite.
Granite is an anagram, meaning that if you take the word 'Granite' and scramble it, it could spell "Tiergan."