2508.50.00.00 - Andalusite, kyanite and sillimanite

This HTS category, 2508.50.00.00, specifically encompasses andalusite, kyanite, and sillimanite. These are naturally occurring aluminosilicate minerals, characterized by their crystalline structure and high refractory properties. They are valued for their ability to withstand extreme heat, making them crucial raw materials in the production of refractory bricks, ceramics, and specialized industrial applications. Their classification here is based on their mineralogical identity, irrespective of whether they have undergone calcination for further processing.

Unlike sibling categories such as bentonite (2508.10.00.00), fire-clay (2508.30.00.00), other clays (2508.40.01), mullite (2508.60.00.00), and chamotte or dinas earth (2508.70.00.00), this heading is narrowly defined to only include the specific minerals of andalusite, kyanite, and sillimanite. While other categories within heading 2508 deal with various types of clays and manufactured refractory materials derived from them, this particular code isolates these distinct aluminosilicate minerals based on their chemical composition and mineralogical form. The other entries in heading 2508 cover distinct materials with different geological origins or processing states.

As this HTS code represents a leaf node, there are no further subcategories. Classification within 2508.50.00.00 is therefore determined by the definitive identification of the imported material as andalusite, kyanite, or sillimanite, regardless of its specific particle size, purity, or whether it has been calcined. The primary distinction is the presence of these minerals, as opposed to other mineralogical groups or forms of refractory materials.