Sillimanite Grain for Refractories
Sillimanite grains are crushed and sized particles of sillimanite mineral (Al2SiO5) used in refractory castables and ramming mixes. This product falls under HTS 2508.50.00.00 as unprocessed sillimanite, valued for its high melting point above 1600°C.
Import Duty Rates by Country of Origin
Alternative Classifications
This product could be classified differently depending on its characteristics or intended use.
If agglomerated or built-up with binders
Agglomerated or molded forms of these minerals become Chapter 68 articles of stone.
If kaolin-dominated mixtures
Blends primarily of kaolin clays shift to heading 2507 clays.
If pre-formed into refractory shapes
Finished refractory bricks containing sillimanite classify as Chapter 69 ceramic goods.
Not sure which classification is right?
Our AI classifier can analyze your specific product and recommend the correct HTS code with confidence.
Import Tips & Compliance
• Specify grain size distribution (e.g
• 3-6mm) in commercial invoices to justify non-agglomerated status
• Include thermal expansion test data distinguishing from mullite products
• For container shipments, ensure ventilation declarations to prevent moisture absorption affecting classification
Related Products under HTS 2508.50.00.00
Calcined Kyanite Powder
Calcined kyanite is a high-alumina aluminosilicate mineral processed by heating to stabilize its crystal structure, preventing volume expansion during ceramic firing. It is classified under HTS 2508.50.00.00 as calcined kyanite, a form of sillimanite group mineral used primarily in refractory and ceramic applications.
Raw Andalusite Ore
Raw andalusite ore consists of natural andalusite crystals extracted from deposits, typically containing 55-60% alumina. Classified under HTS 2508.50.00.00 as uncalcined andalusite, it serves as a raw material for refractory bricks and high-temperature ceramics.
Calcined Andalusite 55% Al2O3
Calcined andalusite with 55% alumina content is heat-treated to convert partially to mullite, improving thermal shock resistance. HTS 2508.50.00.00 covers this calcined form before further processing into finished refractories.
Kyanite Flour -325 Mesh
Ultra-fine kyanite flour (-325 mesh, <44 microns) used as filler in porcelain insulators and spark plugs. Classified under HTS 2508.50.00.00 as ground kyanite, not chemically modified.
South African Andalusite Lumps
Andalusite lumps from South African Namaqualand deposits, sized 10-100mm, containing 58% Al2O3. HTS 2508.50.00.00 applies to this natural uncalcined mineral export product used globally in steel ladle refractories.
Mullite-Forming Kyanite Concentrate
Beneficiated kyanite concentrate selected for optimal mullite formation during firing, 99%+ purity. Falls under HTS 2508.50.00.00 as processed but uncalcined kyanite per Chapter 25 definitions.