2512.00.00.00 - Siliceous fossil meals (for example, kieselguhr, tripolite and diatomite) and similar siliceous earths, whether or not calcined, of an apparent specific gravity of 1 or less

This HTS category, 2512.00.00.00, encompasses siliceous fossil meals and similar siliceous earths. This includes materials such as kieselguhr, tripolite, and diatomite. These substances are characterized by their high silica content and porous structure, derived from fossilized microorganisms. The classification is further refined by the criterion of an apparent specific gravity of 1 or less, indicating their lightweight and often powdery nature. Both calcined and uncalcined forms of these materials fall within this heading, suggesting that heat treatment for specific properties does not alter their fundamental classification.

While this category is located within Chapter 25, which deals with a wide array of mineral products, it is distinct from other headings that might cover different types of earths or stones. For instance, it would not include materials primarily classified by their use as pigments (e.g., natural ochres) or as abrasives unless they specifically meet the definition of siliceous fossil meals. Similarly, common clays or earths used in construction, such as those for cement or plaster, are classified elsewhere. The key differentiator for this heading is the origin and composition as fossilized silica deposits with a specific gravity characteristic.

As 2512.00.00.00 is a leaf node in the HTS structure, there are no further subcategories that subdivide this specific classification. Therefore, the focus for classification purposes under this heading lies solely on accurately identifying the material as a siliceous fossil meal or earth and confirming its apparent specific gravity meets the stated criterion of 1 or less. This ensures that only materials with the defined physical and geological characteristics are classified here, preventing misclassification with other mineral products.