Tuesday, March 17, 2009
Have you ever picked up a rock, examined it, then stuffed it into your pocket to add to your collection of treasures? Maybe you wondered, "Why does that rock have stripes?" or "Why is it blue?"
Meet some "rockhounds," a term for people who enjoy collecting rocks and minerals. They could easily answer those questions.
In second grade, Alec Brenner enjoyed digging through gravel by his school's playground. Comparing what he found with descriptions in field guides and online, he learned how to tell prehnite, a green mineral, from somewhat similar-looking green calcite.
Soon, he was teaching younger students how to identify rocks and minerals. Alec has been looking for cool specimens ever since.
Last year, Alec, now an eighth-grader, and his teammate, Lauren Bomgardner, both students at Longfellow Middle School in Fairfax County, took first place in the "rocks and minerals" category at the Virginia State Science Olympiad tournament and 11th place in the national competition. "They gave us a list of 93 rocks and minerals to identify, and of course there were some I'd never seen in my entire life," Alec said.
Alec would like to work in the natural sciences or in medical research, fields that require patience and attention to detail -- skills he's learning through being a rockhound.Alex
Alex Kindahl, 12, a rockhound from Mount Airy, is interested in a career in forensic science -- especially uncovering forgeries -- so she's developing a keen eye for detail. Yes, there are occasional forgeries in the rockhound world. For example, howlite, a common mineral, can be dyed to look very much like the rarer turquoise. That's okay if someone wants the look of turquoise without the expense, but it's a forgery if someone tries to pass howlite off as real turquoise.
"The best way to find out about a rock is to look at it up close," Alex said. She first observes with her eyes, then gets a closer look with a magnifying lens or a microscope.
What They Have Learned About Rocks and Minerals
Minerals are inorganic and occur naturally in the earth. They each have distinctive physical characteristics and are the building blocks of rocks. Rocks contain one or more minerals.
Knowing how to identify specific minerals is necessary for anyone going into careers in geology or various fields in chemistry, engineering or forensic sciences.
It's very much like detective work: You look for clues, then compare what you see with pictures and descriptions in a good guidebook.
Rockhounds examine grain, color, crystal formation, weight and luster of each specimen. Luster describes how a mineral's surface looks in light. Is the sample dull or metallic? Is it waxy? Is it bumpy like the surface of a gumdrop, or is it more like glass (that's called vitreous).
Alex and Alec also use the Mohs Hardness Scale to determine a specimen's resistance to scratching. The scale lists 10 minerals -- ranging from the soft, easily scratched mineral talc (1) to the very hard diamond (10). Using these minerals and some handy rated tools -- fingernails (2.5), pennies (3.5), paper clips (4.5) -- rockhounds gain more clues to identifying unknown minerals. Each scratches only minerals lower on the scale. So, if a penny scratches a mineral but a fingernail doesn't, you've narrowed the choices.
Many minerals are named for scientists. Smithsonite was named for James Smithson, a British mineralogist whose wealth made our Smithsonian museums possible.
All potential rockhounds need to beware of the very common leaverite rock. It's a rock that's so plain it's not worth picking up, so "leave-her-right- there."
-- Ann Cameron Siegal