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Rockhounds: kids share the nitty-gritty on rock collecting.


Ciaran Connolly likes to hunt for buried treasure. But not the kind you may think. This 13-year-old is a rockhound--a person who collects rocks. The treasures he's after are glittering gemstones and even meteorites from space.

Ciaran is a member of the Albuquerque Gem and Mineral Club in New Mexico. He found his favorite rock while on one of the club's rock-collecting trips to an abandoned mine. Mines can be dangerous places. The group got permission before exploring and went with an adult guide for safety. Once the group was underground, Ciaran chipped away a rock covered with crystals, like quartz. "It was one of the most beautiful things I've ever seen," he says.

Rockhounding isn't just about finding cool new rocks. It's also a fun way to learn about geology, or the physical history of Earth. Earth is 4.5 billion years old, so there is much history to learn. "Most of that is told in the rocks," says Kendall Hauer, a geologist at Miami University in Ohio.



Rock I.D.

Rocks are made up of one or more minerals. These solid substances are found in nature, usually as crystals. Geologists have identified about 4,000 different kinds of minerals, and new ones are constantly being discovered. That's plenty to keep rockhounds busy for a lifetime.

When rockhounds find an interesting rock, they look closely at its physical properties. Collectors identify a rock based on its color and crystal shape. They also look at the way it reflects light and how the rock breaks.

If still stumped, a rockhound can try scratching a rock with different materials. This allows collectors to rank the rock on the Mohs hardness scale. "Talc, the softest, is a 1 on the scale, and diamond, the hardest, is a 10," says 14-year-old Rachel Shroyer, who belongs to the same rock club as Ciaran.

On a Roll

Studying rocks also provides clues about how they were created. Natural forces such as water and erupting volcanoes constantly reshape Earth. In the process, old rocks are destroyed and new ones are created (see "The Rock Cycle," page 14).

There are three types of rocks--sedimentary (sed-uh-MEN-tuh-ree), igneous (IG-nee-us), and metamorphic (met-uh-MOR-fick). Scientists classify rocks depending on how they form. For example, "Igneous rocks form from cooled magma [melted rock] and are found near dormant volcanoes," explains Casey Long, a 12-year-old rockhound from Modesto, California. Obsidian is a black, glassy igneous rock. It's also a favorite in Casey's collection.


Get Digging

Interested in starting your own rock collection? Check out rockhounds' displays at local gem shows and state fairs. That's how both Ciaran and Rachel got hooked on the hobby. Now these kids are showing off their own collections, which have won several fair ribbons.

"It's also a good idea to join a local rock and mineral club," says Casey. These are great places to meet people who share a love of rocks. If you're lucky, you might even discover something brand new. "Earth is constantly changing, so there will always be new minerals to be discovered," says Rachel. "It's one of my goals to find one of them."

Words to Know

Geologist--A scientist who studies rocks and the physical history of Earth.

Minerals--Solids found in nature with a specific chemical makeup and crystal structure.

Mohs hardness scale--Scale that ranks a mineral's resistance to being scratched.

Sedimentary--Rock formed when small particles are cemented together.

Igneous--Rock formed when melted rock cools and hardens at or below Earth's surface.

Metamorphic--Rock formed when an igneous or a sedimentary rock is changed by heat or squeezed by pressure.

Web Connection

Pyrite's nickname is "fool's gold" because it is often mistaken for the real thing. Can you tell which of the minerals below is real gold and which is fake? Find the answer online at superscience.




In this process, rocks continually change from one type to another. Rocks form deep underground and get pushed to the surface as Earth's crust moves or volcanoes erupt. Wind and water wears away at rocks, and the cycle starts again.


Forms after metamorphic rocks melt to form magma (melted rock), which then cools underground or erupts and cools on Earth's surface.


Forms when metamorphism (heat and pressure) changes sedimentary, igneous, or other metamorphic rocks.


Forms when layers of sediment are squeezed and cemented together.



Set a Purpose

Learn how kids take up rock collecting and what the hobby teaches them about the history of the Earth.


* A fingernail has a hardness of 2.5 on the Mohs hardness scale. This means it can scratch chalk and softer materials. But it could be scratched by a copper penny and other harder materials.

* California was the first state to designate a state rock. The state made serpentine its state rock in 1965. Today, many--but not all--states have chosen an official state rock.

* Meteorite is the only type of rock that is not produced by Earth's rock cycle. That's because this type of rock falls from space. More than 31,000 meteorites have been found on Earth.

Discussion Question

* Suppose you found an interesting rock on the ground. What properties might you use to determine the kind of rock you found? (Possible answers: You could look at the rock's color, texture, and hardness. You could crack the rock open to see what's inside.)


Discussion Question

* If you left a rock on the ground, what do you think would happen to it over a million years? (Answers could include: Water and wind would wear down the rock and the sediments would be deposited back into the Earth from gradual place movement. Deep inside the Earth, new rock would form.)



For more on rock collecting tips, tools, and lesson plans, visit this Franklin Institute's Rock Hounds site.

* To learn about minerals, visit the Mineralogical Society of America's Mineralogy 4 Kids Web site.
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Title Annotation:earth science
Author:Crane, Cody
Geographic Code:1USA
Date:Mar 1, 2010
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