Only calcareous monumental or building stones with an apparent specific gravity of 2.5 or more fall under 2515. Lighter calcareous materials — such as chalk or certain soft limestones — do not meet this threshold and are classified under other headings. Importers should verify the specific gravity of the stone when classification is uncertain.

Subheading 251511 covers marble and travertine in their quarried state or after only rough trimming, while 251512 applies once the stone has been cut by sawing into rectangular or square blocks or slabs. Further processing — such as polishing, profiling, or fabrication into finished articles — moves the product out of heading 2515 entirely.