The heading applies only to siliceous fossil meals and similar earths with an apparent specific gravity of 1 or less. Products exceeding that threshold are classified elsewhere, typically under other mineral or stone headings depending on their composition and processing state.

Diatomite is widely used as a filter aid in brewing, food processing, and industrial liquids, as well as a functional filler in paints and plastics. End use does not affect classification at this heading — the physical characteristics (composition and specific gravity) govern, not the intended application.