Really! And that rock is ... ice!
Dana's System of Mineralogy, the world authority on minerals classifies ice as a mineral, just like granite.
Ice meets all the requirements. It's solid, inorganic, has a definite chemical composition and an ordered atomic arrangement. Meanwhile, because water isn't solid, it isn't a mineral.
In a way it isn't all that surprising because ice looks like some rocks. The picture above isn't of ice, it's a rock -- quartz.
Gives new meaning to a drink "on the rocks."