2508.60.00.00 - Mullite

Mullite, classified under HTS code 2508.60.00.00, refers to a specific synthetic ceramic material. It is a refractory compound composed primarily of aluminum silicate, typically formed by the calcination of mixtures containing alumina and silica. Mullite is valued for its exceptional high-temperature strength, low thermal expansion, and resistance to chemical attack, making it a crucial component in high-performance refractory products, kiln furniture, and specialized ceramic applications.

This classification is distinct from other entries within heading 2508. While siblings like bentonite (2508.10), fire-clay (2508.30), other clays (2508.40), andalusite, kyanite, and sillimanite (2508.50), and chamotte or dinas earth (2508.70) all fall under "Other clays" and related earth materials, mullite is specifically a manufactured product derived from these or similar raw materials through a high-temperature process. Unlike naturally occurring clays or minerals, mullite is engineered for its advanced material properties.

As a leaf node within the HTS, 2508.60.00.00 does not have further subdivisions. Therefore, the focus for classification remains on identifying the material as mullite, distinguishing it from other natural aluminosilicates and refractory earths. Classification hinges on the material's composition and its production method, ensuring it aligns with the definition of mullite as a high-temperature synthetic ceramic.