Final answer:
Major sources of the world's ores and precious metals are found in the Earth's crust as economically extractable minerals, including significant production of cobalt in the Congo and numerous other minerals throughout Europe and the rest of the world. Accessible deposits have been heavily exploited, indicating that future efforts will likely require greater investment.
Step-by-step explanation:
The question asks what are a major source of the world's ores and precious metals. Major sources of the world's ores and precious metals include types of rocks in the Earth's crust that contain economically extractable minerals. These ores are typically found as oxides, sulfides, silicates, or native metals and must be processed to separate the valuable metals from the waste rock. Significant sources of precious metals like gold and cobalt are found in places like the Congo, which leads the world in cobalt ore production, a metal essential for high-performance batteries and medical implants. Moreover, the items such as tin and tungsten contribute to global supply, and Europe is known for its vast deposits of iron ore and other minerals that have supported its industrialization. Despite the abundance, it is important to consider that the supply of these materials is finite, and most easily accessible deposits have already been exploited. Therefore, future mining efforts may require greater investment to continue accessing these resources.