There exists 6 types of processes that lead to the concentration of one or more minerals in rocks which form ore deposits: igneous crystallization, sedimentary processes, metamorphic process, hydrothermal process, biological process, weathering.
For example, the igneous crystallization process led to the formation of magmatic magnetite iron ore deposits and chromium deposits. The iron can also be obtained either from banded iron deposits, which are the results of sedimentary processes, or from hematite deposits, which are the result of weathering process. The aluminum deposits are also the result of weathering process.
The most common ore forming process is hydrothermal process and the copper or lode-gold deposits are the results of this process.
Since the mineral resources are nonrenewable, while the demand for critical mineral resources presents an accelerated increase, the estimation of life of each important mineral reserve becomes a must.
The estimated life, in years, of the aluminum reserves is of 133, while the estimated life of iron reserves is of 75. The estimated life, in years, of copper reserves is of 39, while gold reserves have the shortest estimated life, about 20 years.