Metallica's The Black Album eventually achieved a 2× Diamond certification from the RIAA in the United States.
The Recording Industry Association of America awards a Diamond certification for shipments of 10 million units, so 2× Diamond represents certification for 20 million units. The album first reached platinum status only two weeks after its release, making its later sales milestone especially striking.
The record's continuing success came from both its original run and its long shelf life. Singles such as “Enter Sandman,” “The Unforgiven,” and “Nothing Else Matters” remained central to rock radio and live performances, while the album continued selling across multiple formats.
Certification terminology can cause confusion. “2× Diamond” is not the same as “2× Platinum”: Diamond represents a much larger threshold. Certifications also describe US industry shipments or equivalent units, not a literal worldwide sales total.