U.S. imports of Mullite (HS 250860) totaled $923K in September 2026, imported from 8 countries.
Importers of Mullite paid $27K in duties in September 2026, an average duty rate of 2.94% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule.
Last updated: September 2026 dataMullite is a high-performance aluminosilicate mineral prized in the refractory and advanced ceramics industries for its exceptional thermal stability, low thermal expansion, and resistance to creep at elevated temperatures. It serves as a critical raw material for kiln furniture, furnace linings, and technical ceramic components used in steel, glass, and aerospace manufacturing. The sole US tariff line for this mineral is 2508600000, making classification straightforward, though distinguishing natural from synthetic mullite can affect duty treatment and sourcing decisions.
AI-written summary of the official U.S. Census Bureau trade figures on this page — verify before relying on it.
35 import shipments a month
Mullite is classified specifically under HTS 2508600000 as a naturally occurring or synthetically produced aluminosilicate with a defined crystal structure. Customs may request mineralogical analysis or a certificate of composition to confirm the product meets the mullite specification rather than being classified as a generic clay or other mineral.
The primary demand comes from refractory manufacturers supplying the steel, glass, and ceramics industries, where mullite's high melting point and low thermal expansion make it essential for kiln furniture, furnace linings, and high-temperature structural components.
HS10 import codes under this HS6 parent, each with its own page. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Imports for consumption | Average duty rate | Dutiable Share | Duty Collected |
|---|---|---|---|---|---|
| 2508600000 | Mullite | $814K | 6.92% | 50.71% | $56K |
HS10 export codes under this HS6 parent, each with its own page. Source: U.S. Schedule B export classification.
| Code | Description | Export Value |
|---|---|---|
| 2508600000 | Mullite | $801K |
Import lines come from the U.S. Harmonized Tariff Schedule and export lines from Schedule B. The two are numbered by different agencies, so the same 10-digit code can appear in both tables describing a different product.
Subheading 2 of 6 in heading 2508
Subheading 250860 · $923K of $2.8M
Imports · September 2026
origin
Canada and Germany together supply 91% of it. Germany pays 10.0% duty; Canada 0.0%.
customs district
destination
entry
rate provision · imports
70.6% enters free of duty; duty collected equals 2.94% of imports for consumption.
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ImportsExports
Imports
$923KYoY · free account
Exports
—YoY · free account
12-mo low · imports
Low · free accountOver the twelve months to September 2026, the U.S. imported $10.2M of Mullite.
Through September 2026 · exports 11 of 12 months reported. Source: U.S. Census Bureau.