WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
25.19 - Natural ma nesium carbonate (magnesite); fused magnesia; dead-burned (siutered) magnesia, wBether or not containing small quantities of other oxides added before sintering; other magnesium oxide, whether or not pure. 25 19.10 - Natural magnesium carbonate (magnesite) 2519.90 - Other This heading $overs magnesite (or giobertite) which is a naturally occurring magnesium carbonate w t h Impurities xn various proportions. The heading also covers various types of magnesia (magnesium oxide) obtained from natural magnesium carbonate, basic magnesium carbonate, magnesium hydroxide precipitated from sea water, etc. The main types are : (I) Fused magnesia, obtained by fusion. It is usually colourless but may be slightly yellowish or greenish. It is less soluble than other types of magnesia and is used, for example, in the manufacture of crucibles or heating elements for electric ovens. A (2) Dead-burned (sintered) magnesia, obtained by high temperature about 1400-1800 OC) calcination. Sintered rnapesla may contain small quantities of o er oxides (e.g., iron oxide or chromium oxide), added before sintering in order to lower the sintering temperature. It is used in the manufacture of refractory bricks. (3) Caustic-burned magnesia, usually obtained fiom rnagnesite by relatively low temperature (lower than 900 "C) calcination. It is more chemically reactive than fused or sintered magnesia and is used, for example, in the production of magnesium compounds, decolouring agents or oxychloride cement. Light and heavy magnesium oxides are usually obtained by calcination of pure precipitated magnesium hydroxide or basic carbonate at temperatures from 600 OC to 900 "C. These magnesium oxides are practically insoluble in water but are readily soluble in dilute acids and are more chemically reactive than other types of magnesia (i.e., sintered magnesia and fused magnesia). They are used in the manufacture of medicaments, cosmetics, etc. The heading does not cover : (a) Hydrated basic ma esium carbonate, sometimes known as " pharmacist's magnesia " (heading 2&6). white @) Cultured cystals (other than optical elements), of magnesium oxide, wei hing not less than 2.5 g each (headu~g38.24); optical elements of magnesium oxide (heading 90.08
1.- Except where their context or Note 4 to this Chapter otherwise requires, the headings of this Chapter cover only products which are in the crude state or which have been washed (even with chemical substances eliminating the impurities without changing the structure of the product), crushed, ground, powdered, levigated, sifted, screened, concentrated by flotation, magnetic separation or other mechanical or physical processes (except crystallisation), but not products which have been roasted, calcined, obtained by mixing or subjected to processing beyond that mentioned in each heading. The products of this Chapter may contain an added anti-dusting agent, provided that such addition does not render the product particularly suitable for specific use rather than for general use. 2.- This Chapter does not cover : (a) Sublimed sulphur, precipitated sulphur or colloidal sulphur (heading 28.02); (b) Earth colours containing 70 % or more by weight of combined iron evaluated as Fe O 2 3 (heading 28.21); (c) Medicaments or other products of Chapter 30; (d) Perfumery, cosmetic or toilet preparations (Chapter 33); (e) Dolomite ramming mix (heading 38.16); (f) Setts, curbstones or flagstones (heading 68.01); mosaic cubes or the like (heading 68.02); roofing, facing or damp course slates (heading 68.03); (g) Precious or semi-precious stones (heading 71.02 or 71.03); (h) Cultured crystals (other than optical elements) weighing not less than 2.5 g each, of sodium chloride or of magnesium oxide, of heading 38.24; optical elements of sodium chloride or of magnesium oxide (heading 90.01); (ij) Billiard chalks (heading 95.04); or (k) Writing or drawing chalks or tailors' chalks (heading 96.09). 3.- Any products classifiable in heading 25.17 and any other heading of the Chapter are to be classified in heading 25.17. 4.- Heading 25.30 applies, inter alia, to : vermiculite, perlite and chlorites, unexpanded; earth colours, whether or not calcined or mixed together; natural micaceous iron oxides; meerschaum (whether or not in polished pieces); amber; agglomerated meerschaum and agglomerated amber, in plates, rods, sticks or similar forms, not worked after moulding; jet; strontianite (whether or not calcined), other than strontium oxide; broken pieces of pottery, brick or concrete.