Koshertopia has cofirmed that The Diamond Dairy, a kosher hotspot in the Diamond District ( in the back mezzanine of the jewelry exchange on 4 W. 47th Street) has closed its doors for good.  For close to 60 years, the diner, a hidden gem in the Diamond Distrcit, had been serving up Ashkenazic style Jewish food to the many emloyees in the area as well as many tourists and passersby.