In mining, valuable minerals are found in rocks known as ore. The "grade" tells us how much of the valuable mineral is in the ore, usually shown as a percentage or in grams per ton. For example, a grade of 75% means that 75% of the ore's weight is valuable mineral. Similarly, a grade of 2.5 grams per ton (g/t) means there are 2.5 grams of the valuable mineral in each ton of ore. Grade isn't the same everywhere in a mining deposit—some areas have higher grades, some have lower, and some may have none at all. Higher grades mean more valuable minerals and higher profits, while lower grades yield less revenue. If the grade is too low, the costs of mining and processing can exceed the revenue, leading to losses. The "cut-off grade" is the minimum grade that makes mining profitable. Anything below this grade is considered waste.