Magnesia (Unslaked): IMSBC Code Schedule and Carriage
The MAGNESIA (UNSLAKED) schedule under the IMSBC Code, Group B with MHB codes SH and CR, and how it differs from the Group C MAGNESIA (DEADBURNED) entry.
MAGNESIA (UNSLAKED) is a Group B cargo carrying the MHB notation SH and/or CR. Its Hazard cell states that it combines with water to form magnesium hydroxide with an expansion in volume and a release of heat, that it may ignite materials with low ignition temperatures, and that it is corrosive to eyes and mucous membranes. The Code itself grades it against quicklime, describing it as similar to LIME (UNSLAKED) but less reactive.
The full article will set out the schedule cell by cell and will contrast it against MAGNESIA (DEADBURNED), which is Group C. The split between the two is a matter of what the product is rather than where a particular parcel sits on a reactivity scale: deadburned magnesia is natural magnesite calcined at very high temperatures, giving a non-reactive magnesium oxide which does not hydrate or produce spontaneous heat, and its only precaution is a declaration from the shipper or manufacturer that the cargo has been sufficiently heat-treated and is ready for loading.
It will also address the naming trap. Calcined magnesia in commercial usage generally means the deadburned Group C product, so a fixture describing a cargo as calcined magnesia and a schedule assigning it Group B are describing different things, and only the Bulk Cargo Shipping Name on the declaration resolves it.