You arrive at the white spire.

The door glides open, and you notice a hall of luminous white marble. Chandeliers float resuspended, illuminating the place. A grand staircase spirals upward, and the wizard descends with a glass of wine in his hand. He wears a black tuxedo with a fancy red shirt, but his face is ugly, with a huge nose, small eyes, and bizarre proportions. He welcomes you with an elegant gesture.
"The divination says that a rare individual will enter my tower today. What can I do for you?" he says.

You explain your quest, and he says that you have to be careful. The church is crazy about the stone, and you should not be talking about that, or you could be in trouble.

Then he says that he can help you, but he will not do it for free, he's a businessman.

You can try to convince him with your knowledge and maybe help him with his research.
You can also pay with a quest, something that you can do for him, like a common adventurer.