2519.90.20.00 - Caustic calcined magnesite

This HTS classification, 2519.90.20.00, specifically covers caustic calcined magnesite. Caustic calcined magnesite is produced by heating natural magnesium carbonate (magnesite) at relatively low temperatures (typically below 1000°C). This process drives off most, but not all, of the carbon dioxide and water, leaving a reactive form of magnesium oxide. It retains a significant degree of its original crystalline structure and is characterized by its high reactivity, making it suitable for various industrial applications, particularly in the production of magnesium compounds, refractories, and as a neutralizer in chemical processes.

This category is distinguished from its sibling, 2519.90.10.00, which encompasses fused magnesia and dead-burned (sintered) magnesia. While all originate from magnesite, fused and dead-burned magnesia are produced through higher temperature sintering processes (above 1000°C and significantly higher for fused magnesia). These higher temperatures result in a less reactive, more dense, and highly refractory material, primarily used for high-temperature applications. Caustic calcined magnesite, in contrast, is intentionally produced to maintain a higher level of chemical activity.

As a leaf node, 2519.90.20.00 has no further subcategories. Therefore, classification within this specific code relies on confirming the material is indeed magnesite that has undergone calcination to a "caustic" or reactive state, as opposed to the more fully calcined or fused forms found in sibling categories. The key distinguishing factor for this code is the temperature of calcination and the resultant chemical reactivity of the magnesium oxide.