As others have said - Brunello is what the locals in Montalcino call Sangiovese - right down the road in Scansano - they call it Morellino -
I am willing to be called a pedant: The word you wanted is variety, not varietal.
Can all Grosso clones be called Brunello or does the term only apply to the original Biondi-Santi clone (B-BS-11 otherwise known as Sangiovese FPS-12)? Looking at the national grape registry, it seems that they only use the term Brunello for the clones that are or trace directly to B-BS-11. Other grosso clones are noted as Grosso di Montalcino.