oregrades

Ore grades are a measure of the concentration of economically valuable minerals within an ore. They are used to assess the viability of mining projects and to design processing flows. Grades are commonly expressed as percent for metals such as copper, grams per tonne (g/t) for precious metals like gold, or parts per million (ppm) for other constituents. For example, an ore with 5 g/t gold contains 5 grams of gold per tonne of ore.

Ore grades vary within and between deposits and influence mining decisions. Not all ore with a high grade is economical to mine if recovery is low or processing is expensive. The cut-off grade is the minimum grade at which ore is included in production; it is determined by metal price, costs, and desired margins. Grade distributions often feature pockets of higher grade within a lower-grade matrix, affecting blasting, transportation, and processing planning.

Grade is estimated from sampling, drilling, and assaying, using geostatistical methods to interpolate grade between data points. Reconciliation compares predicted grade to actual mined material and refined models. Practical handling includes grade control during mining and blending to meet processing specifications. Ore processing performance depends on both grade and metallurgical recovery, as some high-grade ore may yield less metal if recovery is poor.

Understanding ore grades requires attention to uncertainty, sampling bias, and the distinction between resource grade, reserve grade, and economic cut-off grade. Grade data underpin decisions from exploration to mine closure and are central to assessing project value.