Science World
Science World for grades 6–10 brings science to life with fascinating feature articles and hands-on activities that reinforce science concepts and help students build test-taking and critical-thinking skills.

Jade Hunter

George Harlow climbs up a steep mountainside. The air is dry and the sun intense, but Harlow doesn't let the harsh conditions get to him. He is on a mission, and nothing-not even the poisonous snakes and stinging plants that surround him-can keep Harlow from his goal. He has come to the Central American country of Guatemala in search of an ancient source of the gemstone jade.

Harlow is curator of one of the world's great gems and minerals collections at the American Museum of Natural History in New York City. Here in Guatemala, he transforms into a "jade hunter" - a jadero.

Jade has been treasured around the world for thousands of years. Many of the ancient cultures of Central America used a type of jade, called jadeite, in their art. One of these cultures, the Olmec, is recognized as being the earliest workers of jade in the New World. For centuries, however, local Guatemalans and geologists were unable to confirm the source of the Olmec jade-that is, until Harlow and his team arrived.

Jadeite is found in just 12 places around the world. It is unique among gemstones because of its toughness and beauty. Scientists aren't sure of the exact geological conditions that cause jade to form, but Harlow and his team are digging up answers.

Jade comes in a variety of colors. Pure jade-composed of sodium, aluminum, silicon, and oxygen-is white. Other colors form when small amounts of color-causing elements, such as iron, chromium, and manganese, enter the basic mineral. Apple-green jade, which forms in the presence of chromium, is the most prized of all the colors. Harlow is in Guatemala in search of a blue-green jade with white speckles. This Olmec jade contains titanium and iron.

He and other geologists knew that a blue-green jade existed because they had seen ancient Olmec artifacts crafted from it. But in the 16th century, Spanish conquerers wiped out the Central American indigenous cultures, and knowledge of the location of the jade sources was lost.

Geologists like Harlow know that jade forms at high pressures and low temperatures. They also know that these conditions occur deep inside Earth at places where tectonic plates (giant moving rock slabs that make up Earth's outer shell) collide. So to find jade, scientists look for faults. Faults are breaks in the bedrock where rocks slide past each other during earthquakes. This movement can bring jade to the surface.

In the 1950s, jade was discovered along the Motagua fault in Guatemala. Three decades later, Harlow described sources of white, green, and black jade there. But no one had found the blue-green jade.

Then, in 1999, pieces of the mysterious blue-green jade began showing up in Guatemalan marketplaces. Geologists wondered: Had local Guatemalans suddenly found the lost source of Olmec jade?

Harlow knew that Hurricane Mitch, a storm that devastated Guatemala and the nearby country of Honduras, had moved over the area of the Motagua fault the previous year. He thought the flooding rain might have exposed jade that was previously buried in riverbeds.

With help from local jaderos, Harlow and his team found newly exposed jade; some showed streaks of blue-green color. Harlow's team worked with the jaderos to get small samples of the mineral to bring back to the museum so they could study it further.

When Harlow returned from his expedition, he studied the jade samples to determine their makeup and origin. The samples show similarities with the Olmec jade, but more analysis needs to be done before its origin is determined with certainty.

The samples have also led Harlow's team to discover that the formation of jade is connected to the formation of the kind of volcanoes that are active in Central America.

by Ben Leach

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