6815.91.00 - Containing magnesite, magnesia in the form of periclase, dolomite including in the form of dolime, or chromite

This HTS classification covers articles made from mineral substances that are not elsewhere specified. Specifically, it includes articles primarily composed of or containing magnesite, magnesia in the form of periclase, dolomite (including dolime), or chromite. These materials are often used for their refractory properties, making the articles suitable for high-temperature applications in industries such as steel production, cement manufacturing, and glass making. The classification extends to finished or semi-finished goods where these minerals form a substantial part of their composition.

Distinguishing this category from its sibling, 6815.99, is crucial. While 6815.99 encompasses "Other" articles of mineral substances not elsewhere specified, this sub-heading (6815.91) is specifically for those articles *containing* the listed minerals (magnesite, periclase, dolomite, or chromite). The presence and significant proportion of these specific minerals are the defining characteristics that place an article under 6815.91, rather than a more general mineral-based article.

Within this classification, further subdivisions exist to refine the classification based on specific material composition and manufacturing processes. Subcategory 6815.91.00.11 is designated for articles containing a high percentage of magnesia (over 70%) and bound by resin or pitch, indicating a specific manufacturing technique and material blend. Subcategory 6815.91.00.71 serves as a residual category for all other articles meeting the primary criteria of this heading but not fitting into the more specific sub-classifications.