Native metal

A native metal is any metal found in its pure, metallic form within nature. Most metals do not stay pure because they react with their environment. However, some elements can exist alone as single metals or as alloys. An alloy is a mixture of two or more metals.

This group includes many elements like iron, copper, and zinc. It also includes the gold and platinum groups. Understanding native metals helps us see how different elements resist or succumb to natural changes.

Most metals undergo a process called oxidation when they are exposed to the environment. Over geological time scales, natural weathering processes usually change metals into different compounds. Only a few metals are less reactive, meaning they do not change easily. Gold and platinum are primary examples of these stable metals. Other metals, such as nickel or chromium, appear in much smaller amounts. They often occur in isolated pockets. This happens when a natural chemical process reduces a common ore. This reduction leaves the pure metal behind as small flakes or tiny inclusions.

Gold is the most well-known native metal. It is the predominant gold mineral on Earth. Gold can be found as nuggets, wires, or veins within a rock matrix. It can also appear as fine grains mixed in river sediments. Because gold has a great density, it is very heavy. This allows people to use gold panning to separate gold from lighter sediments.

Gold is sometimes alloyed with silver to form electrum. While gold compounds are rare, gold can occasionally be found as selenides or tellurides.

Silver is another common native metal, though it is more reactive than gold. Silver can appear as irregular masses or elongated dendritic coatings. It also forms distinct crystals, such as cubes, octahedrons, or dodecahedrons.

Silver often occurs alongside silver sulfide or sulfosalt minerals. It can also form alloys with gold, known as electrum. In rare cases, silver and mercury form amalgams. One specific mineral example is eugenite, which is an Ag11Hg2 compound. Because silver reacts more easily, there are many more silver compound minerals than pure native silver.

Copper is a highly significant native metal for human history. An ancient North American civilization called the Old Copper Complex used it. They lived near Lake Superior between 6000 and 3000 BC. They mined native copper to make weapons, tools, and decorative objects.

Copper was more useful than gold because it is stronger. It was hard enough to make fishhooks and woodworking tools. Yet, it remained soft enough to be easily shaped. In the Michigan Copper Country, some native copper masses weighed hundreds of tons. This region was a leading U.S. producer from 1845 until 1887.

Iron is a metal that is rarely truly native to Earth. Most iron found on our planet actually comes from iron-nickel meteorites. These meteorites formed millions of years ago in the vacuum of space. The vacuum protected the metal from chemical attack. When they fell to Earth, they brought alloys like taenite and kamacite.

True telluric iron, which is born on Earth, is extremely rare. There is only one major deposit known near Disko Island in Greenland. Native nickel has also been found through hydrothermal alteration in places like New Caledonia.

Many other metals exist in the native state in very small quantities. For example, metallic cadmium has been found at only two locations, including the Vilyuy River basin in Siberia.

Native molybdenum has even been discovered in lunar regolith on the moon. Other elements like antimony, bismuth, and arsenic also occur this way. While metals are the most famous, non-metals can also be native. Carbon, sulfur, and selenium are examples of non-metallic elements found in this pure state. Even the semi-metal silicon has been found as tiny inclusions in gold.