Cost per tonne (C/t) is one of the most fundamental and widely used financial performance metrics in the mining industry, expressing the total cost of mining, processing, or transporting a unit mass (one metric tonne) of material — whether ore, waste rock, or final product — across a defined scope of operations. In bauxite, gold, iron ore, and diamond mining, cost per tonne is a critical key performance indicator (KPI) used by mine managers, financial analysts, and investors to assess operational efficiency, plan budgets, track cost trends, and compare performance across different operations or time periods. Cost per tonne calculations can be applied at multiple levels of the mining value chain: mining cost per tonne (total cost of drilling, blasting, loading, hauling, and grade control, divided by the total tonnes of ore and waste mined); processing cost per tonne (total cost of crushing, grinding, leaching, flotation, smelting, or other processing activities, divided by tonnes of ore processed); and total cash cost per tonne of product (all direct costs divided by tonnes of finished product sold, such as tonnes of alumina produced in bauxite refining, or ounces of gold produced expressed as a cost per ounce). The components of cost per tonne typically include labour, energy (diesel and electricity), consumables (grinding media, reagents, explosives, tyres), maintenance and repair, contractor costs, and allocated overhead. In iron ore mining, where operations are extremely high volume and margins are often thin, cost per tonne is a fiercely competitive metric and small improvements can have a significant impact on profitability. In gold mining, cost per tonne of ore processed is tracked alongside the grade (grams per tonne) to determine the all-in cost per ounce of gold produced. In diamond mining, cost per tonne of ore treated is compared to the recovered grade (carats per hundred tonnes, or cpht) to determine the cost per carat. Regular analysis of cost per tonne trends, and comparison against budget and against peer group benchmarks, is a central activity in mining financial management and operational excellence programs.
