Dry metric tonne

A dry metric tonne is a unit used in mineral concentrate contracts equal to one tonne of material after its moisture has been removed.

Mineral concentrate carries moisture along with the valuable ore, and buyers do not want to pay concentrate prices for water weight. A dry metric tonne is the unit that solves this: it is one tonne of material after its moisture content has been measured and subtracted out, so payment reflects only the dry material actually delivered.

Copper and other metal concentrate contracts are priced per dry metric tonne of contained metal, determined by combining the concentrate’s total dry weight with an assay of its metal content. This unit, often abbreviated DMT, is specific to the concentrate trade; refined metal like cathode is simply weighed and sold by ordinary tonne, since it carries no meaningful moisture to account for.