2508.40.01 - Other clays

This HTS category, "Other clays," encompasses a broad range of argillaceous materials that do not fit into more specific classifications within heading 2508. These include clays that exhibit various geological origins and physical properties, excluding expanded clays which are classified under heading 6806. The classification here is primarily based on the absence of specific defining characteristics that would place them under categories like bentonite or fire-clay, and distinct from the aluminosilicate minerals like andalusite.

Unlike its sibling categories, "Other clays" is a residual classification. Bentonite (2508.10) is specifically defined by its high montmorillonite content, fire-clay (2508.30) by its refractory properties, and andalusite, kyanite, and sillimanite (2508.50) are distinct mineral forms. Similarly, mullite (2508.60) and chamotte or dinas earth (2508.70) represent specific calcined or refractory materials. Therefore, "Other clays" serves as a catch-all for clays that do not meet the precise criteria of these specialized groups.

Within the "Other clays" heading, further subdivisions distinguish between common and specialized types. Subcategories include "Common blue clay and other ball clays" (2508.40.01.10), which are typically plastic and used in ceramics. "Decolorizing earths and fuller's earth" (2508.40.01.20) are distinguished by their adsorptive properties, often used in refining oils. Finally, "Other" (2508.40.01.50) accounts for any remaining clays that do not fall into these more specific sub-classifications under "Other clays."