There may be a bit of legend and myth in this illustration but it is essentially true. The comment by the student is unverifiable. 

A sculptor had ruined a huge piece of beautiful Carrara marble. It was left in the courtyard of the cathedral in Florence, Italy, for 40 years. Artisans thought it was beyond repair. But in 1505, a young sculptor by the name of Michelangelo was asked if he thought anything could be done with "The Giant." He measured the block and carefully noted the imperfections caused by the bungling workman of an earlier day. To his mind came the image of the young shepherd boy David. So he carefully made a sketch of that biblical character as he envisioned him. For 3 years he worked steadily, his chisel skillfully shaping the marble. Finally, when one of his students was allowed to view the towering figure, 17 feet high and weighing 9 tons, he exclaimed, "Master, it lacks only one thing, and that is speech!"

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Facts from History.com: Michelangelo was notoriously picky about the marble he used for his sculptures, yet for his famous “David” statue, he made use of a block that other artists had deemed unworkable. Known as “the Giant,” the massive slab had been quarried nearly 40 years earlier for a series of sculptures, eventually abandoned, for the Florence Cathedral. It had deteriorated and grown rough after years of exposure to the elements, and by the time Michelangelo began working with it in 1501, it already bore the chisel marks of more than one frustrated sculptor. Michelangelo eventually crafted the discarded block into one of his most luminous works, but recent analyses of the “David” have revealed that the poor quality of its stone may have caused it to degrade at a faster rate than most marble statues.