2508.70.00.00 - Chamotte or dinas earth

This HTS category, 2508.70.00.00, specifically covers chamotte and dinas earth. Chamotte is a refractory material derived from calcining fireclay. Dinas earth, also known as silica refractory or Dinas brick, is a highly siliceous refractory material made from quartzite or quartz sand, usually with a small amount of lime as a binder. These materials are primarily valued for their ability to withstand extremely high temperatures and their use in the production of refractories for furnaces, kilns, and other high-temperature industrial applications.

While belonging to the broader group of "Other clays" and related refractory minerals under heading 2508, chamotte and dinas earth are distinct from its sibling categories. Bentonite (2508.10) is a clay of the smectite group, primarily montmorillonite, known for its absorbent properties. Fire-clay (2508.30) refers to clays with a high alumina and silica content that can withstand high temperatures, but it is generally the raw material for chamotte. Andalusite, kyanite, and sillimanite (2508.50) are naturally occurring aluminosilicate minerals that transform into mullite upon heating, exhibiting refractory properties. Mullite (2508.60) is the synthetic product formed from the calcination of these minerals or fireclay, also used in refractories. Chamotte and dinas earth are distinct processed forms of refractory materials, characterized by their specific composition and preparation for high-temperature service.

As a leaf node within the HTS, 2508.70.00.00 does not have further subdivisions. Classification within this code is based on the material's identity as either chamotte (calcined fireclay) or dinas earth (high-silica refractory material). The primary distinguishing factors are the source material and the manufacturing process that imparts its specific refractory characteristics, differentiating it from raw clays or other processed refractory minerals in adjacent subheadings.