>> IDAHO IS CALLED THE GEM STATE.

DO YOU KNOW WHY?

IT'S A TREASURE TROVE FOR PEOPLE INTERESTED IN ROCKS AND MINERALS.

DO YOU WANT TO KNOW MORE?

WE HAVE SCIENTISTS READY TO TAKE YOUR QUESTIONS.

EMAIL OR CALL IN.

"D4K," "DIALOGUE FOR KIDS" IS NEXT.

>> LLO, I'M JOAN CARTAN-HANSEN.

THANK YOU FOR JOINING US HERE ON IDAHO PUBLIC TELEVISION AND ON THE WORLDWIDE WE GEOLOGY IS THE STUDY OF ROCKS AND MINERALS.

TO UNDERSTAND ROCKS, YOU FIRST NEED TO KNOW HOW ROCKS ARE MADE AND WHAT THEY'RE MADE OF.

AND WHERE DO YOU START?

LOOK OUTSIDE YOUR DOOR OR YOUR WINDOW.

IDAHO'S BEAUTIFUL MOUAINS MAY LOOK REALLY SOLID.

BUT LIKE ALL ROCKS, THEY'RE CONSTANTLY CHANGING.

IT HAS TO DO WITH THE ROCK CYCLE.

THERE ARE THREE MAJOR TYPES OF ROCKS.

IGNIIUS IS FORMED WHEN MAGMA COOLS AND IS SOLID.

THIS CAN HAPPEN BELOW THE ROCK'S SURFACE OR CLOSER TO THE RFACE.

MOST OF THE EARTH IS MADE UP OF THIS KIND OF ROCK.

SEDIMENTARY ROCKS ARE FORMED WHEN STUFF LIKE SAND AND DIRT ARE PUT DOWN IN LAYERS.

THEN SQUEEZED BY A LARGE AMOUNT PRESSURE UNTIL THE LAYERS BECOME SOLID.

OVER 75% OF THE EARTH'S LAND'S SURFACE IS COVERED BY SEDIMENTARY ROCK.

MET A FOR PHIL MICKELSON ROCKS ALREADY EXIST, BUT WERE TRANSFORMED BY HEAT OR PRESSURE.

AS SOON AS ROCKY MOUNTAINS ARE FORMED THEY BEGIN TO CHANGE.

ROCKS BREAK DOWN INTO SMALLER PIECES THROUGH WEATHERING.

HEAT, WIND, WATER FREEZING AND THAWING CAN ALL WEAR AWAY AND CRACK APART ROCKS.

PLANTS AND ANIMALS BREAK UP ROCKS TOO.

THE PARTS OF THE ORIGINAL ROCKS ARE REMOVE BY EROSION OR BLOWN AWAY TO A NEW LOCATION.

WHEN THE DEPOSITS ARE BURIED, HEAT AND PRESSURE MAKE THEM INTO NEW ROCKS.

AND THE ROCK CYCLE BEGINS ALL OVER AGAIN.

HOW ROCKS ARE FORMED IS ONE WAY TO CLASSIFY OR IDENTIFY ROCKS.

ANOTHER WAY IS TO FIGURE OUT WHAT IT'S MADE OF.

A ROCK IS MADE UP OF ONE OR MORE MINERAL.

MINERALS ARE MADE UP OF ONE OR MORE OF 92 DIFFERENT NATURAL ELEMENTS THAT COMBINE TOGETHER IN DIFFERENT WAYS.

SOME ROCKS LIKE GOLD AND DIAMONDS ARE VERY VALUABLE.

AND OTHERS ARE, WELL, USEFUL FOR A GOOD SKIPPING STONE.

ROCKS TAKE A LONG TIME TO FORM, AND THEY'RE ALWAYS CHANGING.

WE LIVE ON THEM, BUILD OUR HOMES OUT OF THEM, EVEN WEAR THEM.

ROCKS AND MINERALS ARE ESSENTIAL TO OUR LIVES.

JOINING ME NOW TO ANSWER YOUR QUESTIONS ABOUT ROCKS AND MINERALS ARE TWO GUESTS.

SCOTT HUGHES IS INTERIM DEAN OF IDAHO STATE UNIVERSITIES COLLEGE OF ARTS AND SCIENCES AND THE CURRENT CHAIR OF I.S.U.

'S DEPARTMENT OF GEOSCIENCES.

HE JOINS US FROM OUR POCATELLO STUDIO.

THANK YOU FOR JOINING ME.

>> GREAT TO BE HERE.

I'M LOOKING FORWARD TO THESE QUESTIONS.

>> HERE IN BOISE IS VIRGINIA GILLERMAN, A GEE ONLY GIST WITH THE IDAHO GEOLOGICAL SURVEY.

OF COURSE WE WANT TO HEAR FROM YOU.

GIVE US A CALL TOLL-FREE AT 1-800-973-9800.

OR EMAIL ME AT D4K@IDAHOPTV.ORG.

REMEMBER, WHEN YOU SEND IN A QUESTION, YOU AND YOUR CLASS WILL HAVE A CHANCE TO WIN A D.V.D.

PLAYER AND OTHER PRIZES.

LET'S GO TO OUR FIRST QUESTION FROM THE FOURTH GRADE CLASS AT CYNTHIA MANN ELEMENTARY.

AUSTIN WOULD LIKE TO KNOW HOW MANY DIFFERENT KINDS OF ROCKS ARE THERE.

WE DISCUSSED THE THREE MAJOR TYPES.

>> THERE'S PROBABLY AT LEAST A COUPLE DIFFERENT THOUSAND KINDS OF ROCKS, BUT EVERY ONE IS UNIQUE.

ROCK IS COMPOSED OF A MIXTURE OF MINERALS, AND IF YOU'VE LOOKED AROUND OUTDOORS YOU MIGHT NOTICE EVEN THE GRANITE IN CENTRAL IDAHO LOOKS A LITTLE DIFFERENT FROM ONE PLACE TO THE NEXT.

SO THERE'S JUST THOUSANDS OF DIFFERENT TYPES OF ROCKS.

THERE'S PROBABLY MAYBE SCOTT HAS A FIGURE, I WOULD SAY AT LEAST 300 NAMES SORT OF NAMED CATEGORIES OF ROCKS BETWEEN THE THE THREE YOU MENTIONED.

>> I WOULD SAY THAT'S A GOOD NUMBER.

AT LEAST 300.

BUT THE INTERESTING THING IS THAT WE TRIED TO PUT ROCKS INTO CLASSIFICATIONS, AND WE SAY THIS ROCK IS SUCH AND SUCH, THIS ROCK IS SUCH AND SUCH, WHEN ACTUALLY THERE'S A BROAD SPECTRUM AND A BROAD RANGE, SO THERE'S NOT MUCH DIFFERENCE BETWEEN ONE ROCK AND ANOTHER, BUT THEY MIGHT HAVE TWO COMPLETELY DIFFERENT NAMES.

>> LET'S TALK ABOUT COLORS OF ROCKS.

RICHARD WANTS TO KNOW WHAT KIND OF CLORLS OF ROCKS ARE THERE?

>> THE COLOR OF ROCKS DERIVES FROM THE COLOR OF MINERALS.

THE COLOR OF MINERALS DERIVES FROM WHAT KIND OF ATOMS ARE IN THOSE MINERALS AND HOW THEY ARE PUT TOGETHER IN A REGULAR ATOMIC ARRANGEMENT.

AND SO ONE MINERAL MIGHT BE VERY GREEN, AND ANOTHER MINERAL MIGHT BE ALMOST DARK BROWN OR BLACK, AND SO THE ROCK ITSELF THAT THEY'RE -- THAT ARE MADE UP OF THOSE MINERALS MIGHT BE A VERY DARK GREENISH BLACK.

OTHER TIMES WE HAVE MINERALS THAT ARE VERY LIGHT COLORED, ALMOST WHITE.

AND THE COLOR OF THE ROCK THEN TAKES ON THE COLOR OF THOSE MINERALS.

>> LET'S GET OUR FIRST PHONE CALLER IN HERE.

ALL DECENT FROM BOISE.

ARE YOU THERE, ALDEN.

>> Caller: WHAT?

>> GO AHEAD.

GO AHEAD AND ASK YOUR QUESTION.

LOOKS LIKE WE LOST HIM.

THE QUESTION WAS, WHAT MAKES CERTAIN ROCKS VALUABLE?

>> WELL, I BROUGHT IN A FEW ROCKS THAT ARE VALUABLE.

THEY'RE USUALLY VALUABLE EITHER FOR THEIR BEAUTY AND THEIR DECORATIVE VALUE, OR ELSE FOR VALUABLE ELEMENT THAT THEY CONTAIN.

GOLD IS THE ONE THAT YOU MIGHT BE THINKING OF, BUT I HAVE AN EXAMPLE OF SILVER ORE FROM NORTH IDAHO, AND ONE FROM CENTRAL IDAHO, THE SILVER MINERAL HERE.

MANY TIMES WE GET MANY VALUABLE THINGS FROM THE EARTH WE DON'T ALSO APPRECIATE.

THIS ONE IS USED IN JET ENGINES AND LUBRICANTS AND IS AN IMPORTANT INGREDIENTS IN MANY SPECIALTY STEELS.

AND SO OVEN IT'S THE USE OF SOMETHING, WHETHER IT BE SAND OR GRAVEL, OR GOLD, THAT MAKES IT VALUABLE.

>> AND JEFFREY, WHO IS HOME SICK TODAY, SORRY, JEFFREY, SENT IN A QUESTION, WHY ARE ROCKS SO HARD?

>> YOU KNOW, ROCKS ARE HARD BECAUSE OF THE WAY THEIR ATOMS ARE BOUND TOGETHER.

FOR EXAMPLE, YOU MIGHT HAVE A ROCK THAT'S MADE UP OF A MINERAL THAT HAS, LIKE, CARBON.

CARBON IS ONE OF THOSE ELEMENTS THAT IF IT'S BOUND A CERTAIN WAY, IT MAKES A VERY SOFT MINERAL CALLED GRAPHITE.

BUT IF IT'S BOUND A DIFFERENT WAY, IT CAN BE SO HARD, IT BECOMES THE HARDEST MINERAL KNOWN TO HUMANS, WHICH IS CALLED DIAMOND.

AND SO THE REASON ROCKS ARE HARD ARE, NUMBER ONE, HOW HARD THEIR MINERALS ARE, AND NUMBER TWO, HOW THOSE MINERALS ARE BOUND TOGETHER.

AND SO A NICE GRANITE CAN BE VERY HARD BECAUSE IT'S MINERALS ARE INTERGROWN AND LOCKING VERY TIGHTLY.

WHEREAS A ROCK LIKE A SANDSTONE THAT MIGHT NOT HAVE ITS MINERALS PACKED TOGETHER TOO TIGHTLY COULD BE VERY SOFT.

>> LET'S GO TO BRANDON IN MERIDIAN.

GO AHEAD AND ASK YOUR QUESTION.

>> Caller: WHAT IS THE MOST VALUABLE ROCK, AND WHAT WAS THE ROUND ROCK THAT HAD THE STAR ON IT WITH THE SQUARE NEXT TO IT?

>> YOU'RE NODDING YOUR HEAD, VIRGINIA?

>> THE MOST VALUABLE ROCK CERTAINLY DIAMONDS WOULD BE A CANDIDATE.

THE ROUND ROCK THAT THEY SHOW THE PICTURE OF AT THE BEGINNING OF THE SHOW WAS A STAR GARNETT.

AND THAT'S OUR STATE GEMSTONE.

AND IT IS VERY VALUABLE.

TOTALLY FOR DECORATIVE PURPOSES.

STAR GARNETTS ARE FOUND IN NORTHERN IDAHO AND ALSO IN THE COUNTRY OF INDIA.

SO THEY'RE PRETTY RESTRICTED IN THEIR LOCATION.

AND THEY'RE VALUED FOR THEIR BEAUTY.

>> EMERALDS, TOO.

REALLY GOOD QUALITY EMERALD CAN BE MORE VALUABLE THAN DIAMONDS.

>> IT IS.

EMERALDS, NATURAL AQUA MARINE, THAT'S BECAUSE THEY'RE SO RARE, AND BECAUSE IN A GEMSTONE, YOU HAVE TO LOOK AT THE COLOR, THE CLARITY, OF COURSE HOW BIG IT IS, THE LARGER ONES, THE VALUE SORT OF GROWS EXPONENTIALLY.

AND TO GET AN EMERALD WHICH IS FREE FROM INCLUSION AND DEFECTS, AND TO HAVE IT BE A GOOD COLOR IS EXTREMELY RARE.

SO THEY'RE EXTREMELY VALUABLE.

>> LET'S GO TO EMILY IN JEROME.

EMILY?

>> Caller: HI.

>> GO AHEAD.

>> Caller: I WAS WONDERING IF WHEN LAVA TOUCHES ROCK, DO THEY MELT, OR WHEN ACID TOUCHES A ROCK, CAN IT DISSOLVE?

>> WELL, SOME ACIDS ARE VERY CORROSIVE, AND CAUSE A LOT OF REACTION.

FOR EXAMPLE, HYDROCHLORIC ACID IS A FAIRLY WEAK ACID, BUT IT WILL ATTACK LIMESTONE OR THE MINERAL THAT LIMESTONE IS MADE OF, CALLED CALL SITE, VERY EASILY.

AND IT WILL CAUSE IT TO DISSOLVE IMMEDIATELY.

IF THE SAME ACID IS PUT ON TO QUARTS, THAT WILL SIT THERE FOR THOUSANDS OF YEARS AND NEVER GO AWAY.

SO SOME MINERALS ARE VERY RESISTANT TO ACID AND SOME ARE NOT.

ANOTHER TYPE OF ACID THAT'S VERY CORROSIVE IS SULFURIC ACID.

IF YOU MIX THAT WITH A MINERAL THAT HAS A LOT OF SULFUR IN IT, THE REACTION MIGHT BE VERY STRONG.

HOWEVER, THERE'S ONE ACID CALLED HYDROFLOUR I CAN ACID THAT IS SO STRONG, EVEN QAWTS WILL FIND ITSELF IN TROUBLE IF IT COMES IN CONTACT WITH HYDROFLOURIC ACID.

WE CANNOT KEEP THOSE IN GLASS JARS, BECAUSE THE GLASS JARS WOULD BE EATEN UP.

THEY HAVE TO BE KEPT IN PLASTIC JARS.

>> A QUESTION FROM A CLASS AT HORIZON ELEMENTARY IN BOISE, TAYLOR WOULD LIKE TO KNOW, CAN DIAMONDS MELT?

DIAMONDS ARE THE STRONGEST ROCK, BUT CAN THEY MELT?

>> YES, THEY COULD, IF YOU COULD GET IT HOT ENOUGH.

I DON'T OFFHAND KNOW WHAT THE MELTING TEMPERATURE OF DIAMOND IS, BUT OF COURSE ANY SUBSTANCE HAS A SOLID, A LIQUID, AND A GASEOUS FORM.

AND THAT'S ESSENTIALLY WHAT MELTING IS, GOING FROM THE SOLID TO THE LIQUID.

I WOULD THINK IT WOULD BE PRETTY HIGH PRESSURE, BUT I'VE NEVER DONE THAT EXPERIMENT.

MAYBE SCOTT HAS.

>> WELL, IF YOU'VE MELTED A DIAMOND, IT WOULD BE WORTHLESS AFTER THAT, BECAUSE IT WOULD JUST BE A BLOB OF CARBON LIQUID, AND THERE'S NO WAY TO MAKE IT BACK INTO A DIAMOND, THAT'S FOR SURE.

>> LET'S GO TO ANOTHER QUESTION FROM MRS.

GRIS'S CLASS AT HORIZON ELEMENTARY.

IF DIAMONDS ARE THE STRONGEST ROCK, WHAT'S THE SECOND STRONGEST?

>> WELL, FIRST OF ALL, DIAMOND IS A MINERAL.

AND SO THE STRONG -- THE HARDEST MINERAL IS DIAMOND.

THE NEXT HARDEST ONE WOULD BE CORRUNDUM.

I THINK VIRGINIA HAS GOOD IDEAS ABOUT WHAT TYPES THERE ARE, AND SHE WOULD LET YOU KNOW, MOSTLY ALUMINUM OXIDE, BUT ALL DIFFERENT VARIETIES MAKE MINERALS THAT WE FIND IN -- AS GEM STONES IN THIS STATE AND OTHERS.

>> THAT'S CORRECT, SCOTT.

SEVERAL WELL-KNOWN VARIETIES OF THAT STONE WOULD INCLUDE THE GEM RUBY, WHICH IS OF COURSE RED, EMRALDZ, WHICH ARE GREEN.

THERE IS JUST BASIC NONGEM QUALITY CORRUNDUM, WHICH IS MAYBE NOT VERY COMMON, BUT NOT AN UNCOMMON CONSTITUENT OF TYPICAL METAMORPHIC ROCKS LIKE WE HAVE IN NORTHERN IDAHO.

AND IT HAS A HARDNESS OF NINE ON WHAT'S CALLED THE CAME OF HARDNESS, WHICH GOES FROM 1-10.

>> FROM JESSE, SHE WANTS TO KNOW WHY ARE SOME LAVA ROCKS RED, AND SOME BLACK?

WHY ARE SOME OF THEM RED, AND SOME OF THEM BLACK?

>> WHEN LAVAS FLOW, LIKE THE LAVA FLOES WE SEE IN HAWAII, THEY MIGHT BE RED BECAUSE THEY'RE HOT AND GLOWING, BUT AS THE LAVA COOLS, THE LAVA WILL BECOME A BLACK OR AN ORANGE, OR A RED, OR BROWN, DEPENDG ON E OXIDATION STATE.

IRON, AS YOU KNOW, IF YOU TAKE YOUR DAD'S HAMMER AND YOU THROW IT OUT IN THE YARD AND LEAVE IT OUT IN THE RAIN AND SO FARTSDZ, IT -- FORTH, IT GETS RUSTY, AND IT TAKES ON A DIFFERENT COLOR THAN THE NICE SHINY STEEL THAN WHEN HE BROUGHT IT HOME FROM THE HARDWARE STORE.

WHEN LAVA COOLS, SOME OF THE GASSES REACT WITH THE IRON IN THE LAVA TO CHANGE THE ALTERATION -- CHANGE THE STATE OF OXIDATION OF THAT IRON, AND SO SOME MUCH IT COMES OUT RED, THAT'S REALLY OBJECTION DICED, AND SOME OF IT COMES OUT BLACK, WHICH IS NOT SO OXIDIZED.

>> LET'S GO TO MONTANA LEWISTON.

GO AHEAD AND ASK YOUR QUESTION.

>> Caller: WHAT'S THE BIGGEST GEM IN THE WORLD?

>> WOW.

LET'S SEE.

THERE ARE SOME GEMS THAT ARE QUITE LARGE.

I DON'T RECALL THE LARGEST, SAY, DIAMOND THAT'S FOUND, BUT THEY COULD BE ON THE ORDER OF FIST SIZE.

>> THE HOPE DIAMOND IS THE WEST THAT'S MOST FAMOUS.

>> THAT WAS -- IT'S A COUPLE OF HUNDRED KARATS CUT, BUT OF COURSE IT WAS PROBABLY SEVERAL, MAYBE A COUPLE OF THOUSAND KARATS BEFORE IT WAS CUT AND FACETTED INTO A CUT GEMSTONE.

ON THE OTHER HAND, THERE'S QAWRTS CRYSTALS I'VE SEEN IN MUSEUMS THAT ARE ALMOST GEM QUALITY, AND SOME OF THOSE YOU COULD GET ONE THAT WAS A FOOT LONG, AND SIX, EIGHT INCHES ACROSS.

NEEDLESS TO SAY, THAT'S PRETTY HAIR.

SOME OF THE LARGEST GEMSTONE CRYSTALS COME FROM BRAZIL, AND YOU MAY HAVE SEEN SOME OF THOSE IN ROCK STORES OR IN A MUSEUM OR SOMETHING.

THESE AM THISES -- >> THOSE ARE COOL.

I'VE GOT SYDNEY WHO WOULD LIKE TO KNOW IF A KID CAN MAKE A ROCK.

CAN YOU ACTUALLY MAKE A ROCK?

SURE.

YOU COULD MAKE A ROCK.

BUT IT WOULD NOT BE A NATURAL ROCK, OF COURSE.

BUT THERE ARE VARIOUS WAYS.

THE EASIEST ROCK TO MAKE WOULD BE A SEDIMENTARY ROCK, WHERE YOU ALLOWED THE SEDIMENT TO SETTLE OUT AND SIT FOR A LONG TIME DEWATERING, BUT YOU'D HAVE TO PUT PRESSURE UNDER IT.

IF YOU FOUND YOURSELF A NICE BIG PRESS AND SQUEEZED IT, IT MIGHT NOT BE A VERY GOO ROCK, BUT IT WOULD BE ONE THAT WOULD BE BETTER THAN JUST LOOSE SEDIMENT LYING AROUND.

SURE, YOU CAN MAKE A ROCK.

>> LET'S GO TO SEBASTIAN.

SEBASTIAN IN NAMPA.

GO AHEAD.

>> Caller: HOW DO ROCKS FORM IN THE OCEAN?

>> WELL, IT WOULD BE SORT OF A NATURAL EXAMPLE OF THE KIND OF ARTIFICIAL ROCK SCOTT WAS JUST TALKING ABOUT.

IN THE OCEAN, ROCKS CAN FORM IN TWO GENERAL WAYS.

ONE, THEY CAN BE WHAT WE CALL CHEMICAL PRECIPITATES, LIKE A LIMESTONE THAT MIGHT RESULT FROM CRYSTALLIZATION FROM DISSOLVED CALLS NUMBER CARBONATE PARCELS -- PARTICLES THAT COLLECT TOGETHER, AND THEN DROPS TO THE BOTTOM OF THE OCEAN AND FORMS AS LAYERS OF LIMESTONE.

THE OTHER WAY, WHICH IS PROBABLY EASIER TO SEE, IS, FOR EXAMPLE, ON A BEACH WHERE YOU HAVE A SANDY BEACH, AND OVER TIME IF THE OCEAN SORT OF RETREATS, THAT SAND LAYER WILL GET BURIED BY OTHER PLAYERS OF SEDIMENT, AND EVENTUALLY OVER MILLIONS OF YEARS COMPRESSED INTO WHAT COULD BE A VERY HARD ROCK.

IN THE BUY SI FOOTHILLS WE HAVE SANDSTONE THAT WAS PROBABLY A LAKEFRONT BEACH, AND WE CAN HAVE FINER GRAIN SEDIMENTARY UNITS AS WELL.

THAT WOULD CERTAINLY BE AN EASY ONE TO THINK ABOUT.

>> WE'VE GOT BEAUTIFUL MOUNTAINS IN IDAHO, AND WE'VE GOT A QUESTION ABOUT THE IDAHO BATHELITHUANIAN.

HOW OLD IS THE IDAHO BATHELITHUANIAN?

>> I KNOW I'M GOING TO GET MYSELF INTO TROUBLE HERE.

IS THAT A MESOSOIC PLIEW TON?

>> IT IS.

AND A GENERAL RANGE WOULD BE IN THE 70 TO 100 MILLION-YEAR RANGE.

THERE'S SEVERAL DIFFERENT PLUTONS WITH SLIGHTLY DIFFERENT AGES THAT -- >> WHAT'S A PLUTON?

>> IT WOULD BE A SMALLER PORTION OF TH BATHELITH.

WHICH IS AN IGNIUS MASS WHICH ORIGINATED AS MOLT YEN -- MOLTEN ROCK OR MAG THAT PLACED IN THE EARTH'S CRUST AND COOLED SLOWLY.

A PLUTON IS A MORE GENERIC CATEGORY, A SMALL PLUTON, FOR EXAMPLE.

>> LET'S TRY JOSHUA IN BOISE.

JOSHUA?

>> HOW DO ROCKS GET THEIR SHAPE?

>> WELL, NOW, ROCKS ARE FORMED BY THOSE THREE DIFFERENT TYPES OF PROCESSES, AND SO DEPENDING ON THE PROCESS, A ROCK WILL HAVE PROPERTIES MAKING IT SOFTER IN ONE DIRECTION, AND HARDER IN ANOTHER DIRECTION.

OR IT MIGHT BE -- HAVE SOME TEXTURE WHICH WE SAY FOLIATED OR LYNN YAITED OR LAYERED, OR WHATEVER.

AS ROCKS BREAK, THEY BREAK ALONG PLANES OF WEAKNESS, AND SO DURING THE WEATHERING PROCESS, WHICH WOULD, SAY, MECHANICAL WEATHERING, THE ROCKS ARE BROKEN UP, AND THE SHAPE DEPENDS ON HOW STRONG THEY ARE IN VARIOUS DIRECTIONS.

ON THE OTHER HAND, A ROCK MAY BE WASHED OVER WITH WATER AND ERODED DOWN, AND SO THE SURFACE OF THAT ROCK MIGHT BE CHANGED JUST BECAUSE THE EFFECT OF EROSION.

SO THERE ARE MANY DIFFERENT WAYS OF GETTING DIFFERENT SHAPES OF ROCKS.

BUT PRIMARILY IT ALL DEPENDS ON THE PROPERTY OF THE ROCK ITSELF AND HOW STRONG IT IS IN ONE DIRECTION VERSUS ANOTHER.

>> LET'S GO TO ALEXANDRA IN BOISE.

ALEXANDRA?

GO AHEAD?

>> Caller: HOW DO YOU FIND THE AGE OF A ROCK, AND HOW ACCURATE IS THAT?

>> WELL, THERE'S TWO MAIN WAYS GEOLOGISTS DETERMINE THE AGE OF A ROCK.

THE FIRST WAY, OF COURSE, WAS WITH FOSSILS.

AND FOSSILS REPRESENT OLD ANIMALS OR PLANTS THAT EVOLVED IN CERTAIN DIRECTIONS AND PALEONTOLOGISTS HAVE STUDIED THAT OVER THE YEARS, AND DETERMINED WHAT WERE THEN RELATIVE AGES OF THESE PLANTS AND ANIMALS, AND THUS THE ROCKS THAT THEY WERE FOUND IN.

MORE RECENTLY SCIENTISTS USE RADIOMETRIC AGE DATING OF ROCKS.

AND THAT'S A CONSEQUENCE OF THE DECAY OF CERTAIN UNSTABLE ISOTOPES OF SOME ELEMENTS.

>> BECAUSE YOU CAN TELL THE AGE OF THE URANIUM WITHIN THE ROCK -- >> RIGHT.

THEY DECAY AT A UNIFORM CONSISTENT RATE.

AND BY MEASURING CERTAIN ISOTOPES WITHIN THE ROCK AND DOING SOME MATHEMATICS, YOU CAN CALCULATE AN AGE OF THE ROCK.

SO LIKE WE THINK THE EARTH IS ABOUT 4.5 BILLION YEARS, WE CAN DETERMINE AGES OF ROCKS THAT ARE AS YOUNG AS 50,000 YEARS ON THE SNAKE RIVER PLAIN, FOR EXAMPLE.

IT'S A LOT MORE COMPLICATED THAN THAT.

>> YOU BROUGHT -- YOU BOTH BROUGHT A FEW ROCKS.

WHAT DO YOU HAVE HERE?

>> I BROUGHT SOME EXAMPLES OF FIRST OF ALL MINERALS.

HERE'S A MINERAL THAT SHOWS A NICE CRYSTAL HABIT.

THIS IS PIE RIGHT.

-- PYRITE.

>> FOOL'S GOLD.

>> IT HAS AN UNUSUAL FORM.

AND HERE'S ANOTHER EXAMPLE OF A MINERAL, THIS IS THE MINERAL FLOURITE, WHICH OCCURS IN DIFFERENT COLOR BANDS, GOING FROM GREEN TO PURPLE, AND THEN THERE'S A LAYER OF PYRITE ON TOP.

>> I LOVE THE GREEN COLOR.

AND THEN THERE'S GOLD ON THE TOP.

>> AND THEN I'VE GOT SOME MINERALS FROM IDAHO THAT ARE USED FOR VARIOUS THINGS.

THIS ONE, THE SILVERY MINERAL IN THERE IS TETRAHEDRIFE.

IT'S AN IMPORTANT SILVER ORE.

THIS ONE IS FROM I BELIEVE FROM THE IDAHO MERCURY MINE, THE PINK MATERIAL IS THE MINERAL CINNABAR.

AND I THINK I MENTIONED THIS ONE FROM CENTRAL IDAHO.

AND THESE TWO ARE ROCKS.

AND NOTICE THAT THEY'RE COMPOSED OF A COLLECTION OF MINERALS.

THIS ONE MAY BE HARDER TO SEE, BUT IT'S PART OF A BAND IRON FORMATION FROM MICHIGAN.

AND IT TELLS A STORY OF IRON-RICH SEDIMENTARY LAYERS THAT WERE FOLDED AND METAPHORPHOID INTO HEMATITE AND SILICA.

>> I HAVE A HEMATITE NECKLACE IT.

>> CAN BE USED FOR IRON ORE FOR STEEL, AND JEWELRY AS WELL.

THIS IS ONE FROM NEVADA, WHICH TELLS A STORY.

THERE'S TWO ROCK TYPES, ONE IS A GRANITE, AND THE OTHER E IS A VOLCANIC ROCK.

YOU CAN SEE THERE'S A QUARTZ VEIN WHICH CUTS THE GRANITE, BUT IS CUT OFF WITH THE CONTACT WITH THE RYELITE.

SO QUESTION KNOW THERYELITE WAS YOUNGER THAN THE AGE OF THE QUARTZ VEIN.

THAT'S AN EXAMPLE OF HOW WE CAN USE ROCKS TO TELL STORIES.

THAT'S THE PART I FIND FASCINATING.

>> THIS IS MY FAVORITE QUESTION OF THE DAY -- CAN THE HUMAN BODY DIGEST ROCKS?

>> CAN THE HUMAN BODY DIGEST ROCKS?

IF YOU HAVE ENOUGH TIME, YOUR STOMACH HAS LOTS OF GOOD ACIDS IN IT, AND IT CAN DIGEST MANY THINGS, BUT QUITE OFTEN THERE'S A TIME FACTOR, AND IF THE ROCK -- IF CERTAIN ROCKS HAD MANY, MANY YEARS TO SIT IN YOUR STOMACH, IT MIGHT WORK.

HOWEVER, YOUR BODY PASSES MATERIAL THROUGH VERY QUICKLY, AND SO THE ONLY KIND OF ROCKS THAT MIGHT BE DISSOLVABLE ARE CONSUMED BY HUMANS WOULD BE SOMETHING THAT'S VERY EASILY DISSOLVED IN WATER.

FOR EXAMPLE, ANYTHING WITH SALT IN IT, AND SALT MAKES THE MINERAL HALITE, WHICH IS A VERY SOFT MINERAL, AND IT'S DISSOLVABLE.

AND SO YOU MIGHT SEE OUT IN THE PASTURE COWS LICKING ON A SALT LICK.

YOU MIGHT HAVE AT SOME TIME IN THE PAST.

THERE'S ANOTHER MINERAL IN THAT CALLED SILVITE.

SO YOUR BODY WOULD DIGEST THAT.

HOWEVER, YOU WOULDN'T WANT TO DIGEST TOO MUCH AT ONE TIME BECAUSE IT MIGHT BE BAD FOR YOU.

OTHER THAN THAT, THERE AREN'T TOO MANY MINERALS THAT CAN BE DIGEST AND ABSORBED.

>> WE'RE RUNNING OUT OF TIME.

I WANT TO GET A FEW MORE PHONE CALLS.

IF YOU'RE ON THE LINE, STAY WITH ME, BECAUSE WE'LL BE TAPING OUR WEB EXTRA PROGRAM AS SOON AS THIS PROGRAM IS OFF THE AIR.

IF YOU'RE ON THE LINES, STAY WITH US AND WE'LL GET TO THAT QUESTION.

LET'S GO TO ELSIE FROM HIGHLANDS ELEMENTARY.

WHAT'S THE HEAVIEST MINERAL?

HOW MUCH DOES IT WEIGH?

>> THE HEAVIEST MINERAL, AND IT'S ACTUALLY WOULD BE BASED ON A DENSITY, NOT JUST A WEIGHT, WOULD EITHER BE GOLD OR POSSIBLY I THINK GOLD ITSELF WOULD BE THE HEAVIEST.

I DON'T THINK THERE'S A URANIUM MINERAL OXIDE THAT WOULD BE HEAVIER THAN THAT.

AM I RIGHT, SCOTT?

>> I THINK YOU'RE RIGHT.

THERE AREN'T TOO MANY -- URANIUM IS GOING TO MAKE AN OXIDE, WHICH WILL BE A LOT LIGHTER.

>> LET'S GO TO SHAY IN BOISE.

GO AHEAD, SHAY.

>> Caller: I WAS WONDERING HOW THE SAWTOOTH MOUNTAIN WERE MADE.

>> GOOD QUESTION.

THE SAWTOOTH MOUNTAINS ARE PART OF THE WHOLE IDAHO SYSTEM, AND YOU CAN SEE HOW THOSE PEAKS ARE RISING WAY UP INTO THE AIR.

THAT MEANS THAT THEY WERE PUSHED UP OR THEY ROSE BY SOME SORT OF BUOYANT FORCES AS -- AND WHILE THE MOUNTAINS ARE RISING, THEY GET INTO THE UPPER PARTS OF THE MOUNTAINS, THERE'S A LOT OF SNOW AND RAIN, AND WHEN THE RAIN AND SNOW FREEZES, IT SPLITS THE ROCKS APART.

AND AS THE ROCKS SPLIT APART, THEY BREAK APART AND FALL, AND THEY FALL LEAVING JAGGED RIDGES AND PEAKS, AND SO FORTH.

AND DOWN AROUND THE FOOTHILLS OF THOSE MOUNTAINS YOU'LL SEE WHERE THE ROCKS HAVE BEEN BROKEN UP AND NOW WILL BE INCORPORATED INTO STREAMS.

>> YOU KNOW, WE'RE RAPIDLY RUNNING OUT OF TIME.

IF YOU WANT TO LEARN MORE ABOUT ROCKS AS A CAREER, WHAT SHOULD YOU DO?

>> TALK TO GEOLOGIST.

OF COURSE YOU CAN ALWAYS LOOK ON THE WEB.

RIGHT NOW GEOLOGY, PARTICULARLY SOME OF THE APPLIED FIELDS LIKE MINING AND PETROLEUM, ARE GREAT CAREER OPPORTUNITIES.

GEOSCIENCE IS USEFUL IN ALL KINDS OF ENVIRONMENTAL CAREERS.

IT'S A GREAT CAREER.

>> IF YOU'RE ON THE PHONE LINE, STAY WITH US AND WE'LL RECORD YOU FOR OUR WEB EXTRA.

IF YOU WANT TO LEARN MORE ABOUT ROCKS AND MINERALS, WE'VE GOT MORE INFORMATION ON OUR WEBSITE.

GO TO IDAHOPTV.ORG.

CLICK ON "D4K," YOU'LL FIND OUT IF YOU HAVE A QUESTION, LET ME TELL YOU WE'VE GOT A COUPLE OF WINNERS IN OUR BOOK CONTEST.

WE HAVE CALEB FROM MR.

WALQUEST'S CLASS AT PAUL ELEMENTARY.

AND IN APRIL, GABRIEL IN MR.

HOUCHIN'S CLASS AT JOHN BROWN ELEMENTARY IN RATHDRUM.

THANK YOU FOR SENDING IN QUESTIONS.

THANK YOU FOR JOINING US.

JOIN US ON THE WEB FOR THE REST OF THE SUMMER AND WE'LL SEE YOU BACK IN SEPTEMBER.

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