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Native copper

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Native copper is a unique form of the metallic element copper. Most copper in nature is found in an oxidized state. This means it is mixed with other elements rather than being pure. Native copper is one of the few metals that occurs in its uncombined form. This makes it a very special natural mineral. It is highly valued because it is already a pure metal.

This mineral appears in several different physical shapes. It often forms as irregular masses within the earth. It can also appear as fracture fillings in rocks. In rare cases, it forms specific geometric shapes. These are known as isometric cubic and octahedral crystals. These crystals have very precise and structured forms. Such shapes are much less common than the irregular masses.

The appearance of native copper changes based on its environment. When a surface is fresh, it shows bright colors. These colors include reddish, orangish, or brownish tones. However, the metal usually undergoes a process called weathering. As it sits in the air, it develops a coating. This coating is a green or blue-green tarnish called a patina. This patina is made of a substance called copper(II) carbonate.

Scientists use specific measurements to describe the physical properties of this metal. Native copper has a specific gravity of 8.9. Specific gravity is a measure of how dense the material is. The metal is also relatively soft. It has a Mohs hardness of 2.5 to 3. This scale measures how easily a mineral can be scratched. These physical traits help geologists identify the mineral in the field.

Human history is closely tied to the discovery of these deposits. Pre-historic peoples used native copper as an important ore. Native Americans mined copper at various locations on a small scale. Researchers use a method called isotopic analysis to study this history. This analysis shows that copper trading routes existed throughout North America. These routes allowed native peoples to move the metal across vast distances.

The Keweenaw Peninsula in Upper Michigan contains the largest deposits of native copper. This area is often called "Copper Country" or "Copper Island." Commercial mining in the Keweenaw began in the 1840s. These mines were major producers during the 19th and early 20th centuries. Another important site is Isle Royale in western Lake Superior. Many tons of copper were found there. However, only one of the several commercial mining attempts turned a profit.

Geological forces have also moved these large deposits over time. A long time ago, a glacier moved some native copper. The glacier dragged the metal to the west branch of the Ontonagon River. This river is located upriver from Lake Superior. This movement left behind the Ontonagon Boulder. This massive object is now held by the Smithsonian Institution. It serves as a record of how glaciers shape the land.

While Michigan is famous for its copper, it is not the only location. Another major native copper deposit is located in Coro Coro, Bolivia. This shows that these rare uncombined metals can be found in different parts of the world. Understanding these deposits helps us learn about the Earth's crust. It also helps us understand how minerals form and move through nature.

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