Does a crystal fall in the category of a rock?

A crystal is a form defined by the size and shape of its smallest unit. Steel has several crystalline forms, depending on temper. But steel is not a rock. Aluminum can change into a crystalline form and lose all its strength just by being vibrated. But aluminum is not a rock. Quartz is such a versatile material that it can crystallize in the form of other rocks, and quartz is a rock.

Your question does not have a straight answer, partly because "crystal" can mean so many things, and partly because "rock" is an uncertain category.