I found this image elsewhere on the web, but seems like the book Sam was reading has a mention of dragon glass being a cure for something (red underline mine!):
Is ingesting dragon glass a cure for greyscale? If this is true, it's a very clever easter egg of how Sam will cure Jorah Mormont. We know a cure should exist since Shireen was partly cured / didn't die from Greyscale, and given that she is from Dragonstone, which sits on top of a dragon glass mine, it's all the more likely this is true.
What do you think?