How have Earth’s most extraordinary natural resources driven the rise of civilization? "Treasures of the Earth: Gems, Metals, and Power" is a 3-part series that will take us on a journey deep inside Earth to uncover the mysteries of how these treasures were created, and to explore how they have allowed humankind to progress and build our great civilizations. But even as that quest continues, we are discovering that some of our treasures may soon run out or have unintended consequences that bring new perils. Can our ancient treasures reveal new secrets that will help us solve the problems we face today?

More than 4,000 naturally occurring minerals—inorganic solids that have a characteristic chemical composition and specific crystal structure—have been found on Earth. They are formed of simple molecules or individual elements arranged in repeating chains, sheets, or three-dimensional arrays.

Minerals are typically formed when molten rock, or magma, cools, or by separating out of mineral-rich water, such as that in underground caverns. In general, mineral particles are small, having formed within confined areas such as lava flows or between grains of sediments. Large crystals found in geodes and other rocks are relatively rare.

Mineral deposits add color to the landscape. Minerals have existed since the very beginnings of the Earth, forming as our planet cooled. Many form deep beneath the Earth's surface, but some are found on the surface.

Rocks themselves are made of clusters or mixtures of minerals, and minerals and rocks affect landform development and form natural resources such as gold, tin, iron, marble, and granite.

Silicates—including quartz, mica, olivine, and precious minerals such as emeralds—are the most common class of minerals, as well as the major components of most rocks. Oxides, sulfides, sulfates, carbonates, and halides are other major mineral classes.

Gemstones

Many minerals form beautiful crystals, but the most prized of all are gemstones. Uncut gems often look fairly ordinary–like rocks. It's only when they are cut and polished that they obtain the brilliance and luster that gives them their value.

Historically, gems have been divided into precious and semiprecious classes. There are a number of semiprecious gems, many quite beautiful, but diamonds, rubies, sapphires, and emeralds continue to qualify as "precious." (At one time, amethyst was also considered a precious gem, but large reserves were later found in Brazil, reducing its value.)

Precious gems are formed in different ways and composed of different materials, meaning their appearances vary vastly.

Diamonds, made of carbon atoms, are the hardest natural substance found on Earth. Formed under extremely high pressure hundreds of miles underground, they are found in very few locations around the world.