| 2506 | | Quartz (other than natural sands); quartzite, whether or not roughly trimmed or merely cut, by sawing or otherwise, into blocks or slabs of a rectangular (including square) shape: | | | | |
| 2506.10.00 | | Quartz | | Free | | Free |
| 2506.10.00 | 10 | Sands (other than natural) containing by weight 95 percent or more of silica and not more than 0.6 percent of oxide of iron | t | | | |
| 2506.10.00 | 50 | Other | t | | | |
| 2506.20.00 | | Quartzite | | Free | | Free |
| 2506.20.00 | 10 | Crude or roughly trimmed | t | | | |
| 2506.20.00 | 80 | Other | t | | | |
| 2507.00.00 | 00 | Kaolin and other kaolinic clays, whether or not calcined | t | Free | | $2.46/t |
| 2508 | | Other clays (not including expanded clays of heading 6806), andalusite, kyanite and sillimanite, whether or not calcined; mullite; chamotte or dinas earths: | | | | |
| 2508.10.00 | 00 | Bentonite | t | Free | | $3.20/t |
| 2508.30.00 | 00 | Fire-clay | t | Free | | $1.97/t |
| 2508.40.01 | | Other clays | | Free | | $1.97/t |
| 2508.40.01 | 10 | Common blue clay and other ball clays | t | | | |
| 2508.40.01 | 20 | Decolorizing earths and fuller's earth | t | | | |
| 2508.40.01 | 50 | Other | t | | | |
| 2508.50.00 | 00 | Andalusite, kyanite and sillimanite | t | Free | | Free |
| 2508.60.00 | 00 | Mullite | t | Free | | 30% |
| 2508.70.00 | 00 | Chamotte or dinas earth | t | Free | | Free |
| 2509.00 | | Chalk: | | | | |
| 2509.00.10 | 00 | Crude | t | Free | | Free |
| 2509.00.20 | 00 | Other | t | Free | | 13% |
| 2510 | | Natural calcium phosphates, natural aluminum calcium phosphates and phosphatic chalk: | | | | |
| 2510.10.00 | 00 | Unground | t | Free | | Free |
| 2510.20.00 | 00 | Ground | t | Free | | Free |
| 2511 | | Natural barium sulfate (barytes); natural barium carbonate (witherite), whether or not calcined, other than barium oxide of heading 2816: | | | | |
Harmonized Tariff Schedule of the United States inquiry: no
