Earth’s crust contains many minerals and other materials that are useful to people. To get these valuable natural resources, people must dig into the ground. The holes that they dig are called mines. Some mines are narrow shafts, or tunnels, that go very deep underground. Other mines are large open pits, like canyons. The people who work in mines are called miners.

People dig mines to get such things as diamonds, coal, silver, gold, salt, and many other materials. When a mine provides stone for building, it is called a quarry. Drilling into Earth for petroleum, or oil, is another special type of mining. In this case, the hole in the ground is called a well, not a mine. Usually workers dig mines to search for only one type of material. Sometimes they find other valuable resources, too.

There are many ways to make a mine. One way is by digging underground tunnels. Another way is by removing top layers of soil and rock to create a pit.

Tunnel mines can stretch for miles underground. Sometimes the tunnels open into large rooms. Miners who work deep underground in these rooms use large machines to dig away at the walls. Fresh air, water, and electricity must be lowered down to them from aboveground.

Workers use large earth-moving machines to make pit mines. The machines scrape and dig at the soil until they uncover the minerals. As the machines dig deeper and deeper, they create a huge hole in the ground.

Sometimes miners must use explosives, such as dynamite, to create tunnels or to break up Earth’s hard surface. These explosions also break the materials into smaller pieces so that they are easier to collect.

People have dug mines since prehistoric times. Hundreds of thousands of years ago, during the Stone Age, people dug in the ground to search for flint. Flint is a stone that can be used to make weapons and tools.

The first metal to be mined was copper. The oldest copper mines are in Egypt. Ancient Egyptians dug these mines about 7,000 years ago. By 5,000 years ago, people were also mining tin and combining it with copper to create bronze. This metal was important for making sturdy, long-lasting weapons and tools. Later peoples mined iron to make even stronger tools and weapons.

The ancient Greeks mined (quarried) marble for many beautiful buildings. The ancient Romans had huge mining operations, many in lands that they conquered. During the 1400s and 1500s the Spanish grew rich by mining gold and silver in the Americas.

The first mining operations in what is now the United States started in the 1700s. Meanwhile, in Great Britain coal mining helped to start the Industrial Revolution. This was a time when people began to use machines to make goods. Coal was an important source of power for operating the machines.

In the 1900s many countries worked to make mining safer for miners. Today many people are concerned about pollution and other damage to the environment caused by mining.

Gold has been used as currency and for other purposes for thousands of years. There are different types of gold: Gold bullion is gold in the form of bars or ingots. Gold coins can be in the form of sovereigns, Krugerrands, or any other type of coin which contains gold. Gold bars are like gold bullion, but they are usually smaller in size.

Early civilizations valued gold because it didn't tarnish so that it could be worked into jewelry or other objects and be passed on through generations. Today, gold is valued for its beauty and rarity. It is also widely used in industry. Gold is widely seen as a haven during financial trouble and a hedge against inflation. It tends to hold its value when stocks drop and economies are unstable.

Gold miners used picks, shovels, baskets, pans, sluices, and drills to extract the minerals.

The development of metallurgy began when people realized they could use rocks to make things stronger. Metals were formed by heating an ore inside a furnace until it became liquid. They then poured the metals out of furnaces and made items like pots, pans, and weapons.

During the Middle Ages, many new ores contained more than one metal. For example, some alloys have both silver and gold. These are known as "mixed-metal" ores.

The first person or civilization to discover gold is the Ancient Egyptians. They mined gold in Nubia around 2450 BC. An Egyptian alchemist named Zosimos was the first to find pure gold (24 centuries before Columbus reached the Americas). The discovery of gold is attributed to the ancient Egyptians, who made jewelry out of gold. It was at a time when other metals were scarce and valuable.

Historians agree that the civilization of Ancient Egypt was at its prime and had almost everything under control except when it came to maintaining permanent sources of weight. There was an era when even gold was relatively heavier for them than stone.

Gold has been considered valuable throughout history. Ancient Egypt was one of the first civilizations to use gold for coins, charms, and jewelry making. Egyptians believed that gold had protective powers -- they thought it could ward off demons and evil spirits.

Gold has always been highly prized for its decorative value. It was often used in jewelry and ornamentation by many ancient peoples worldwide, including the Egyptians, Phoenicians, Greeks, Romans, Mayans, Chinese, and Japanese.

The Inca goldsmiths in Spain were called "tumis" (craftsman). Tumis had their guild and were very well respected. Gold, which could be hammered into thin sheets, was used to cover walls and roofs of temples, palaces, and houses.

The most common form of decoration in jewelry was small pieces of gold shaped like animals or made into a pendant. Other forms include earrings, necklaces, bracelets, and hairpins. The most valued material was the knotted cord, which contained all kinds of information about taxation, military service, and production quotas.

The artisans also made many gold tools, such as hammers, chisels, and knives. They even used a technique called "la Zapata" to adapt their designs to different materials to produce weapons and tools.

ed gold to make ornaments, tools, weapons, and more. The Aztecs believed that gold was associated with sunlight and fire -- they used it to make shields, which they believed protected their warriors from harm.

The first gold rush occurred in California when gold was discovered at Sutter's Mill on Jan. 24, 1848. The California Gold Rush brought hundreds of thousands of people from around the world to California in a matter of months. In addition to the lure of striking it rich by finding gold nuggets, people were also attracted by the prospect of getting high-paying jobs in the mining industry.

Over time, miners developed more advanced mining methods and dug deeper into the ground. The first mining technique used during the California Gold Rush was panning for gold using a pan filled with sand and water to separate flakes of gold from the dirt. Miners found that pans worked well when water levels were low but not when they were too high since heavier rocks would sink to the bottom and leave behind pieces of shiny ore that contained little or no gold.

The history of gold mining dates back to the Stone Age and Bronze Age when humans first started using stone tools for mining. Although there are many methods for extracting gold from rock, large-scale industrial mining began in 1848 when rich deposits were discovered in California.

This discovery led to enormous growth in the industry and several more mines being found throughout the area. The discovery of these mines led to an increased interest in mining worldwide.

There are several ways to mine gold, such as using cyanide or mercury. However, these methods are dangerous and harmful to the environment. Instead, gold extraction from its ore is done through smelting. Crushed rock is heated with coke (a carbon source) to create molten metal in this method. The melted metal is poured into molds, where it cools and hardens into pure gold.

Gold is a trendy investment choice. Many people store their money in gold bars or gold coins. It's because gold has historically shown itself to be a good investment option. The price of gold tends to go up when the economy suffers as more investors look for ways to protect their assets.

When times are hard, many people turn to gold to make money by investing in gold stocks or buying and selling actual gold bars or coins.

With the discovery of gold in the early days came some effects, which include:

• Gold rushes were causing an influx of people, which strained state resources and often resulted in violence when there wasn't enough gold to go around.

• Banks could operate smoothly with money that was backed by gold.

Gold has been valued throughout human history for its beauty and utility, as well as its scarcity. The discovery of gold is a topic shrouded in mystery, but it is clear that many people have made their fortunes from precious metal over the centuries.