Final answer:
Metals are rarely found in their elemental form within ores due to past extraction depleting easy-to-mine deposits. Ores must be processed to separate the metal from waste, and the declining ore quality makes extraction more resource-intensive over time.
Step-by-step explanation:
The reason you won't find metal in its pure form within ore is due to the way metals are geologically formed in the Earth's crust. Over time, the easily accessible deposits of metals like copper, gold, and aluminum have been depleted, making mining for these metals more challenging. Metal ores are composed of minerals that contain enough metal to make extraction worthwhile.
These ores typically include oxides, sulfides, silicates, native metals, or even noble metals. While prospecting for gold during the California Gold Rush resulted in the discovery of unreactive gold nuggets, such substantial finds are rare because gold and other metals are often found combined with other substances in the rock. To obtain the metal, the ore must undergo a refining process where the valuable metals are separated from the waste rock.
The decline in surface deposits has led to deeper mining efforts, which are more costly and, depending on the metal, can be quite complicated. This complexity comes from the need to reduce the metal to its free form and varies with the concentration and type of impurities present. With constant mining, the best grade ores are being exhausted, making future extraction an ever more resource-intensive endeavor.