| 2518 |  | Dolomite whether or not calcined or sintered, including dolomite roughly trimmed or merely cut, by sawing or otherwise, into blocks or slabs of a rectangular (including square) shape; dolomite ramming mix: |  |  |  |  | 
| 2519 |  | Natural magnesium carbonate (magnesite); fused magnesia; dead-burned (sintered) magnesia, whether or not containing small quantities of other oxides added before sintering; other magnesium oxide, whether or not pure: |  |  |  |  | 
| 2520 |  | Gypsum; anhydrite; plasters (consisting of calcined gypsum or calcium sulfate) whether or not colored, with or without small quantities of accelerators or retarders: |  |  |  |  | 
| 2520.10.00 | 00 | Gypsum; anhydrite | t | Free |  | Free | 
| 2520.20.00 | 00 | Plasters | t | Free |  | $1.38/t | 
| 2523 |  | Portland cement, aluminous cement, slag cement, supersulfate cement and similar hydraulic cements, whether or not colored or in the form of clinkers: |  |  |  |  | 
| 2523.21.00 | 00 | Portland cement: |  |  |  |  | 
| 2524.90.00 | 40 | Milled fibers, group 3 grades (spinning fibers or equivalent) | t |  |  |  | 
| 2524.90.00 | 45 | Milled fibers, group 4 and 5 grades | t |  |  |  | 
| 2525 |  | Mica, including splittings; mica waste: |  |  |  |  | 
| 2525.10.00 |  | Crude mica and mica rifted into sheets or splittings |  | Free |  | Free | 
| 2525.10.00 | 10 | Split block mica | kg |  |  |  | 
| 2525.10.00 | 20 | Mica splittings | kg |  |  |  | 
| 2525.20.00 | 00 | Mica powder | kg | Free |  | 20% | 
| 2526 |  | Natural steatite, whether or not roughly trimmed or merely cut, by sawing or otherwise, into blocks or slabs of a rect- angular (including square) shape;talc: |  |  |  |  | 
| 2526.10.00 | 00 | Not crushed, not powdered | kg | Free |  | 0.6¢/kg | 
| 2526.20.00 | 00 | Crushed or powdered | t | Free |  | 35% | 
| 2528 |  | Natural borates and concentrates thereof (calcined or not), but not including borates separated from natural brine; natural boric acid containing not more than 85 percent of H3BO3 calculated on the dry weight: |  |  |  |  | 
| 2529 |  | Feldspar; leucite, nepheline and nepheline syenite; fluorspar: |  |  |  |  | 
| 2529.10.00 | 00 | Feldspar | t | Free |  | 49¢/t | 
| 2529.21.00 | 00 | Fluorspar: |  |  |  |  | 
| 2529.21.00 | 00 | Containing by weight 97 percent or less of calcium fluoride | t | Free |  | 13.5% | 
| 2529.22.00 | 00 | Containing by weight more than 97 percent of calcium fluoride | t | Free |  | $5.51/t | 
| 2529.30.00 |  | Leucite; nepheline and nepheline syenite |  | Free |  | Free | 
| 2529.30.00 | 10 | Nepheline syenite | t |  |  |  |