This heading covers only natural borate minerals as extracted, concentrates (whether or not calcined) of such materials, and natural boric acid as obtained by evaporation of the water left after the condensation of the natural vapours escaping from the earth in certain regions (the Italian soffioni), or by evaporating water drawn from underground sources in those regions. However, the heading excludes boric acid containing more than 85 % of H3BO3 calculated on the dry weight (heading 28.10).
The natural borates classified here include :(1) Kernite or tincal, sodium borates also known as "natural borax". (2) Pandermite and priceite, calcium borates. (3) Boracite, magnesium chloroborate. The heading excludes the sodium borate (refined borax) obtained by chemical treatment of kernite or tincal and the sodium borates obtained by evaporating complex brines from certain salt lakes (heading 28.40).
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