Original subtitles

- [Narrator] They are the powerful engine

of the Earth's energy.

- If you fell in there, you could get boiled alive.

- [Narrator] They support the tallest skyscrapers

and are the foundation for over 40 million miles of roads.

- [Man] All of construction has been

based on using crushed stones,

from the early Roman roads to today's interstates.

[dramatic music]

- [Narrator] Whether they're billions of years old

or as young as this morning,

they hold the secrets of the universe.

- [Sarah] There's no way to put a price on them.

- [Narrator] You'll never think of that pebble in your shoe

the same way again.

Now get ready to rock,

on "Modern Marvels: Rock's Greatest Hits."

[dramatic music]

[rock music]

Rocks,

they may be the most underappreciated objects

in the natural world.

But we'd be stone cold out of luck without them.

Besides providing us with shelter,

we extract metal from rocks to construct our machines.

- Whether you're sitting in a chair made of steel

or you're driving a car made of steel,

that steel came from rocks.

- [Narrator] We take heat from them for warmth,

and precious minerals to make medicine.

- We rely on rocks to make soil, to grow plants.

- [Narrator] At one time, we used them for weapons.

They season our food,

and add sparkle and wealth to our lives.

- If you're operating a computer, the silicon chips

that make up an important part of that computer

come from rocks.

- [Narrator] The Earth is one huge ball of rock,

25,000 miles around and over 4.5 billion years old.

But a question, what are the most valuable rocks on Earth?

They very well may be NASA's collection of lunar rocks

located at the Lyndon Johnson Space Center near Houston.

[upbeat music]

They're housed in a special building at the center

which was constructed to quarantine astronauts

and material brought back from the Moon

during the Apollo missions.

The lab is off limits to the general public,

and those who work here must observe

stringent cleanliness protocols

to protect the rocks from any form of earth contamination.

All workers who come in contact with the rocks

must wear a bunny suit.

- The suit that I'm wearing is a nylon clean room suit.

The air that comes into this lab is filtered very well

with very, very small HEPA filters,

so the air stays very clean.

Well, this is the door to the vault

where we keep our lunar samples safe.

This is equivalent to a federal reserve bank vault,

and it's a very, very secure kind of storage.

This is a very substantial door, as you will see.

And inside here,

we keep the samples that are still pristine.

We originally brought back 842 pounds.

And you can see, we have cabinets in here,

and these cabinets have nitrogen gas running through them.

- [Narrator] The nitrogen protects the rocks

from certain elements in the Earth's atmosphere.

- On the Moon there is no oxygen and there is no water.

The minute the lunar samples were to come in contact

with oxygen or water in our atmosphere,

they would begin to oxidize.

Or in simple terms, they would begin to rust.

And the samples, in a few decades,

wouldn't be any good for scientific study.

- [Narrator] Collecting these geological samples from the Moon

was a top priority of the Apollo Missions.

No better clues exist about how the Moon formed and evolved.

To gather the Moon rocks,

the astronauts came equipped with custom designed tools.

- These are tongs.

They worked by squeezing the handle

and the tongs would open,

and this enabled the astronauts to pick up rocks off the ground,

because they really couldn't bend over in their space suits.

- [Narrator] Some of the rocks

the astronauts brought back from the Moon

were similar to those found on Earth.

Many were basalt, a product of volcanic activity.

- [Gary] There were lavas and there were crustal rocks,

like the kinds of rocks we made granite tombstones out of.

- [Narrator] As the crewman

gathered the rocks on the lunar surface,

other rocks, tiny ones, hurtling through space,

added an element of danger to their mission.

Such rocky debris, including meteorites,

also pelts the Earth,

but Earth's atmosphere protects us by disintegrating them

or slowing them down.

The Moon, which has no atmosphere,

exposed the astronauts to the threat.

- [Gary] They come in at such fast speeds,

many times the speed of a bullet,

and the space suits were made in such a way

that they could withstand some of these impacts,

because this mass of these particles is very small.

[astronaut murmuring indistinctly]

- [Narrator] Despite the danger,

none of the Apollo astronauts were injured by the particles.

- [Astronaut] Beautiful, just beautiful.

- [Narrator] Back on Earth,

scientists believe that the rocks recovered from the Moon

posed an entirely different kind of threat.

- We were concerned that perhaps there were bugs

or some sort of Andromeda strain

that might exist on the Moon,

but it was a very rare possibility.

We understood that the radiation environment

and the lack of an atmosphere on the Moon

would make it very difficult for a life to survive.

But you always wanna be cautious in an unknown environment.

- [Narrator] Extensive tests determined

that the Moon rocks contain no hint of alien life.

But as hoped,

they have helped researchers gain many new insights.

Since basalt is a common rock on both the Moon and on Earth,

studying its chemistry was the basis

for a mind-boggling theory on how the Moon itself was formed

over 4.5 billion years ago.

- The leading theory right now for the formation of the Moon

is that very early in solar system history,

a planet or a proto planet the size of Mars

impacted the very early planet Earth.

The Mars-sized planet was shattered.

The core of that Mars-sized body became part of Earth,

and the exterior parts, the crust and the mantle,

were all pulverized,

and all those particles went into orbit around the Earth.

So for a while, the Earth had a ring system.

And then over time,

those particles began to slow down and coalesce.

And after a while,

they had all clumped up, and they became the Moon.

- [Narrator] But what about the six sextillion tons of rock

we call planet Earth?

By the way, that's almost 800 billion tons of rock

for every person on the planet.

What are they?

In simple terms,

rocks are composed of one or more minerals.

Minerals are the most solid material found on Earth

and they always have the same chemical makeup.

There are three basic classifications of rock.

One is igneous, like the rocks found

in the lava fields of the Hawaiian Islands.

- An igneous rock is a rock that's formed from cooled magma,

magma being liquid molten rock that has come to the surface

or near the surface, like you would see in a volcano.

- [Narrator] Another type of rock is sedimentary,

like that found in the Grand Canyon.

- Sedimentary rocks are formed by erosion

making bigger rocks into smaller rocks.

And these smaller rocks,

when they lay on top each other over many, many years,

they cement together until they form a solid rock,

a sedimentary rock.

- [Narrator] The third type of rock is metamorphic.

Metamorphic rock forms

when a preexisting rock type is subjected to heat

and extreme pressure.

This causes a physical or chemical change in the rock.

- It could be an igneous rock, originally,

sedimentary rock originally, or another metamorphic rock.

The word metamorphic, meta means change, morph means form.

So in some fashion has changed in form,

either through a change in the mineralogy

or the hardness of the rock.

- [Narrator] It can take millions of years

for a rock to morph from one form to another.

Yet in our never ending drive to put rocks to use,

we're speeding up the process with technology.

Sometimes we can almost do the impossible.

You ever hear the phrase, sink like a rock?

Well with today's technology, we can reverse that.

- We get some products that actually weigh less than water,

they'll actually float when you put them in water.

- [Narrator] This is lightweight aggregate,

but you won't find it in nature.

This rock has been manufactured at the Stalite Company

in Gold Hill, North Carolina.

[upbeat music]

Composed of sand, gravel and crushed stone,

aggregate is a primary ingredient in concrete.

Without concrete, we wouldn't lay foundations strong enough

for buildings to scrape the sky,

or build titanic dams, or pave the sidewalks

leading to our homes.

However, all aggregates are not created equal.

[upbeat music]

Lightweight aggregate composed of such light,

but strong rocks is meta-argelite,

can make much lighter weight concrete

than traditional aggregate.

And lightweight concrete is desirable

because it can reduce construction costs.

- Lightweight aggregate reduces the weight of the concrete

by 25 to 30%, which allows you to use a lot less foundation,

less reinforcement, less reinforcing steels,

and there's less seismic mass of the foundations as well.

[rock music]

- The rocks that the Stalite Company uses

to produce the lightweight aggregate

come from North Carolina's Gold Hill Quarry,

operated by the Vulcan Materials Company.

- This is our meta-argelite.

It is not a slate actually, but it has a slatey appearance.

It's very hard.

- [Narrator] This rock is so hard,

it has to be blasted out of the ground.

The explosive used is made of ammonium nitrate,

an ingredient also found in yard fertilizers.

The explosives are placed in a pattern

that will create a domino effect when detonated.

- These holes are approximately 46 feet deep.

We drill on a 15 by 17 foot pattern.

[machine whirring]

This is a booster.

Inside the booster will go a cap.

The cap is a non-electric cap.

It is set off by a powder substance inside the tube.

[ground explodes]

The amount of rock that's blasted can vary,

but here we usually get about 30,000 tons out of a shot.

- [Narrator] First stop for these rocks, the rock crusher.

- The rock is dumped onto a feeder.

This feeder is fastened to a set of something called

grizzly bars, and they are like grates

with openings between them.

These things will feed the rock forward.

It allows the smaller rock to fall out

and not go through the primary crusher,

therefore saving energy.

- [Narrator] /Up to 7,000 tons of rock are crushed each day.

That's the weight of a fleet of almost 4,000

mid-sized automobiles.

[rock music]

After crushing, the rocks tumble through several screens

to be sorted,

and are then sent to a rotary kiln.

The kiln is where modern alchemy turns heavy rock

into light.

For it is here that the rock material expands under heat

without losing strength.

- And as it slowly tumbles through the kiln,

the temperature slowly rises up to

about 2,100 degrees Fahrenheit.

And at 2,100 degrees,

the material is actually starting to soften.

And then the gases inside,

basically sulfur dioxide and some other gases, form,

and they try to escape.

And what they do is they create millions

of little non-connected cells,

millions of little air bubbles

that are entrapped inside the aggregate.

Then the material falls and goes through the cooler

and it hardens.

That's how it gets its low weight,

because none of the cells are actually connected,

but there's millions of them entrapped inside the aggregate.

- [Narrator] Stalite then sells the cooled aggregate

to construction firms all over the world

to make lightweight concrete

used in skyscrapers, bridges,

and other major construction projects.

One type of rock dominates our city landscapes.

Carved from nature's majesty,

and to finely cut building blocks

of countless classic structures,

[jackhammer buzzes]

granite is synonymous with hardness and durability.

You can count on it to last,

from the facade of the Empire State Building

to your glistening kitchen countertop.

And it all comes from quarries,

like the Rock Of Ages in Barre, Vermont.

Over 500 feet deep,

the quarry is one of the largest in the world,

noted for both the quality of its rock

and the extent of a deposit.

- Barre stone itself is just an exceptional granite,

probably the finest gray granite yet discovered

anywhere in the world.

The deposit's been measured by sound technology.

It's approximately four miles long,

one and a half to two miles wide,

and it's estimated to be up to about 10 miles in thickness.

- [Narrator] That's a tower of granite,

the height of over 36 Empire State buildings.

The deposit at the Rock Of Ages,

like all granite, is igneous rock.

It formed from magma generated millions of years ago

by friction between tectonic plates deep below the surface.

Less dense than the solid rocks surrounding it,

the molten material rose up through the cracks

in the overlying rock and cooled

into the huge granite deposit.

Granite from the Rock of Ages Quarry has been used

in many of America's greatest buildings and monuments.

- We were very, very proud to be a part

of the fabrication of the national World War II Memorial

on the mall in Washington, D.C.

The steps of the capital building in Washington, D.C.,

are also fabricated from Barre Gray granite.

- [Narrator] Rocks such as granite and marble

are often used as so-called dimension stones.

- The term dimension stone refers to stone

that's cut to be a certain dimensional size,

rather than aggregate that's to be used for crushed stone

and other purposes.

[rock music]

- [Narrator] Often it's taken out of the ground

in giant blocks, weighing as much as 200 tons.

Because granite is so hard,

it takes giant powerful drills and saws to cut into it.

Quarrymen call the process of separating

the granite into blocks, channeling.

To separate a block from the quarry wall,

they first have to cut around the sides

and the back of the block.

One method uses a slot drill.

- A slot drill is an air driven rotary drill.

It is set up so that it drills a vertical hole

up to about 20 feet in depth.

Then the drill rod retracts automatically,

moves over on a tracking mechanism.

We sink another hole in another

until we have a row of closely spaced holes up one side,

across the back, and down the other side.

- [Narrator] Once workers drill these initial sets of holes,

they make another pass at the rock,

drilling out the granite between the holes,

called the web.

[rock music]

But now comes the hard part.

They've gotta separate the bottom

without destroying the equipment.

The process is called undercutting.

It begins by drilling a series of holes

in the bottom of the block

and will end with a huge explosion.

- We use primer cord that's often used as a fuse

in other industries.

Looks like a giant jump rope.

It's on a large reel, like a wire.

It's reamed into the holes with a metal rod

about every other hole.

Then it's tied together electrically

and set off remotely.

- Fire.

[ground explodes]

- [Narrator] Once loosened the slabs are lifted

to the rim of the quarry by giant derricks, or cranes.

The most powerful of the derricks can lift an astounding

200 tons of stone at a time out of the 500 foot deep quarry.

- We lower a cable from a derrick and put it in a loop

around the perimeter of the stone.

We don't go underneath the stone,

because we would have no way of lifting it up

to put the cable underneath it.

So we go around the perimeter,

actually cut a small notch into each of the four corners

of the stone, and draw the cable tightly,

just like a slip knot, so that the harder that the block

pulls on the cable, the tighter it becomes.

- [Narrator] Next, the granite goes to a processing plant

to be cut and polished.

This is where workers craft it into the dimension stones

used for our buildings and homes.

[upbeat music]

The most unusual place the granite might show up

is six feet over your head.

Craftsmen first workout tombstone design and lettering

on a computer.

- Then that design is transferred from paper

to a rubber sheet by the computer.

[mallet pounding]

The rubber sheet is then temporarily adhered, or glued,

to the surface of the granite,

and parts of it are cut away to form a stencil.

- [Narrator] A sand blaster then takes over,

spewing its abrasive under high pressure

at 125 pounds per square inch.

Even granite gives way under this assault.

- The abrasive actually will hit the rubber,

but because it can absorb some of the energy,

it deflects and it bounces away.

- [Narrator] Well, granite earns its reputation

as a tough and versatile player above and below ground.

Some rocks are in demand for their durability and beauty.

It's been a favorite of artists and architects

for centuries, whether used in great works of art,

like Michelangelo's statue of David,

or classic buildings, like the United States Capital

and the Lincoln Memorial.

Marble is one of the most sought after materials

on the planet, and built a global industry

worth more than $50 billion.

- Marble is such a desirable stone

because it unifies two very important things:

the beauty and the strength.

[upbeat music]

- [Narrator] Most marble quarries are above ground,

but the Vermont Marble Company's mine in Danby, Vermont

is the largest underground marble quarry in the world.

Their marble supply here reaches over one mile

into the Earth and is spread over 25 acres.

Marble is a metaphoric rock formed by the alteration

of limestone, or dolomite.

[machines whirring]

It's so hard, they use diamond wire saws to cut it.

Diamonds are the hardest of all rocks,

and one of the few strong enough to cut through marble.

The diamonds are strung on a flexible wire.

- We put it on a certain sequence,

and we start with a spring,

and we slide it on the cable,

and then we use a spacer,

and then we use a pearl,

what we call pearl, because it's round and it's expensive,

and it's got diamonds.

And we do another spacer, a spring,

spacer,

a pearl.

- [Narrator] When the diamond saws blur into motion,

the workers keep their distance in case the wire breaks.

- It's very dangerous work.

We have to be careful where you're standing,

because when the wire breaks you could get hit with pieces

coming off the wire moving at a high rate of speed.

- [Narrator] The workers select

only the highest grade of stone.

- What you're looking at here

is the face of the gallery side area.

And that black, and gray, and brown streak

you see in there is what we call tunnel rock.

It's not the desirable stuff that we're after.

This is actually the stuff that we desire.

This particular block right here is what we call

an imperial marble.

It's some of the finest marble in the world.

[upbeat music]

- [Narrator] Pure white marble is the result

of the metamorphism of very pure limestone.

When mineral impurities are present in the limestone,

they can produce the characteristic swirls and veins

in many varieties of colored marble.

[rock music]

Blocks sliced from the wall can weigh as much

as 1,000 metric tons, and are worth about $10,000

before being processed.

Workers cut them down to about 45,000 pounds

to make them more manageable during transport

to the processing plant.

It too is underground.

Here the marble is cut to the exact dimensions

specified by customers.

Then it is sent to the polisher.

- It has 14 different heads on it,

and it has different abrasives that are put

on to the head, and then the marbles fed through

on a conveyor, and the heads come down,

and each one does its part.

And when it comes out the other side,

you can either have what you call a honed

or a glassy finish.

[relaxed music]

- In the past, the quarry stone has been ordered

for both the Jefferson Memorial

and the United States Supreme Court.

[upbeat music]

Yet another type of rock holds the precious stuff

industry uses to make everything,

from your car, to your appliances, to your paper clips.

But prying it loose requires a lot of water, heat,

- Fire! and noise.

[ground explodes]

Our modern world is built on a foundation of iron.

Mined in 50 countries for its durability,

iron makes up approximately 95% of all metals used today.

- Iron is used to make steel.

We would not have all of the factories, the appliances,

the cars.

None of the things that we know today in modern civilization

would exist basically without iron and iron ore.

- [Narrator] And iron comes from rock like this.

When a rock is valuable enough to be mined for the metals

or minerals trapped within it's called ore.

Minnesota is one of the most iron rich states.

- Minnesota was blessed with a large deposit of iron

called the Biwabic Iron Formation,

and it extends for about 110 miles long from Babbit,

Minnesota down to Grand Rapids, Minnesota.

- The iron ore began forming over 2 billion years ago,

when the area that's now Minnesota

was covered by a shallow sea.

- The iron source was located

to the north of the iron range,

and was from volcanic material that was deposited

into a water filled basin,

and later buried, and heated

and formed into a hard iron formation rock.

- [Narrator] Since the late 19th century,

more than 4 billion tons of ore have been mined

from the Biwabic Formation.

- Iron mining began in 1892

near the town of Mountain Iron, Minnesota.

Then from that point on, more and more mining

came into a place.

The initial mines were underground.

They later turned into open pit mines.

- The most valuable iron ore,

during the days of Minnesota mining, was hematite,

which is nearly 60% iron.

Within six decades, miners had exhausted the rich supply.

- It went through World War I, World War II.

Vast quantities of iron ore were mined to provide steel

for the battleships, and the tanks,

and everything else that went along

with those two war efforts.

And in the process, of course,

a lot of the natural iron ore,

the stuff that you could just mine out of the ground,

was exhausted.

So in the early 1950s, a new process was developed

called the taconite process.

- [Narrator] With about 22% iron content,

taconite ore is nowhere near as rich as hematite,

which could be loaded directly from the ground into steel,

making blast furnaces.

[rock music]

With taconite, the iron content must be extracted

grain by grain, and then concentrated.

Key to the process is taconite's magnetic qualities.

- An important characteristic of the taconite

that's being mined is that the iron is magnetic,

and it can be separated from the non-magnetic material

very easily through magnetic separation.

To illustrate that point,

I'll hold a magnet on to the black material here,

and you'll see that it sticks.

The white material, which is quartz, is non-magnetic,

and the magnet falls off.

- [Narrator] The process of magnetic separation

begins by blasting the stone from out of the ground.

The procedure is similar to that used

for blasting aggregate loose.

- Four, three, two, one, zero, fire.

[ground explodes]

- Large haul trucks carry the blasted rock

to a processing plant.

- This is where we take the blasted ore,

We dump it into this crusher.

It's a giant, gyrating cone that slowly turns.

And as it turns, it crushes the ore against the side wall,

reduces it in size from this blasted material

down to about minus six inches.

[rock music]

- [Narrator] From here, the process involves

reducing rocks to smaller and smaller bits

so the magnetic iron can be extracted.

From the crusher, the rocks go through a series of mills

inside the processing plant.

- So the first stage of grinding is called the rod mill.

And what we do there is we introduce

the crushed ore with water and put it into a slurry form,

which is just a mixture of water with the ground material.

All of our processing is done wet.

So we have to mix water with whatever material we have

to transport it through the process.

And then we feed it into these large mills

that rotate and tumble.

Inside of these mills, we put large diameter grinding rods.

These are about four inches in diameter and 20 feet long.

And as these rods tumble over with the turning of the mill,

they grind the ore into a finer slurry.

- [Narrator] Then the slurry goes through its first set

of magnetic separators,

which attract particles with at least 100 times more power

than the magnet on your refrigerator at home.

- Magnetic separators are large rotating drums

that have permanent magnets inside of them.

The magnetic portion of the ground material

is then picked up and separated

from the non-magnetic portion.

- [Narrator] The particles are then sent to ball mills.

They grind them down to the consistency of face powder.

- We use one and a half inch diameter grinding balls,

which are fed into the mill.

And as they tumble, they grind the ore even finer.

- [Narrator] Not ready yet,

the material then goes through another set

of magnetic separators.

It emerges as a concentrate of about 67% iron.

- At that point in time,

we then start adding some limestone and dolomite

back into the process to make a very special pellet

for our customer.

[upbeat music]

- [Narrator] These pellets are the form in which the iron

will be fed into the blast furnaces.

At first, the concentrate must be dried.

- In that plant, we use vacuum disc dryers

to actually suck the moisture out of this wet concentrate.

- [Narrator] An air blast loosens the particles.

- That concentrate is then fed into what we call

balling discs.

And we spin these discs, and we create these pellets,

which we call green balls.

- [Narrator] Then the pellets are baked in a giant furnace.

- And this is a long, 260 foot furnace

where the pellets are fired at 2,400 degrees Fahrenheit,

and then cooled down as they exit the process.

The pellets have to be hardened to a certain strength

in order for them to withstand the transportation

that occurs between here and the blast furnace.

- [Narrator] The pellets are now over 60% iron.

- When the pellets come off the end of the furnace,

they're quite hot yet.

And when they enter into the stockpile behind us,

they're still at a couple of hundred degrees.

From here, the pellets are loaded into rail cars

and shipped down to a port on Lake Superior.

From there, the pellets are loaded into boats,

where they begin their journey down to the blast furnaces

at the Southern end of Lake Michigan.

- [Narrator] In the blast furnaces,

the pellets are melted into molten iron.

[rock sizzling]

Some furnaces using the pellets

can produce over 10,000 tons of molten iron a day.

From here, the molten iron will go to foundries

where the steel is made to build our world.

As rocks rich with iron demand a complex process

to extract their treasure,

another kind of invaluable rock comes pre-fabricated

by nature.

[rock music]

When it comes to rocks, bigger doesn't always mean better.

The smallest rocks of all, sand and gravel,

are crucial ingredients in construction projects

requiring asphalt or concrete.

- Typically asphalt is in the range of 95% stone products.

Concrete is about 80%.

For a single family home, it's about 400 tons of stone.

- [Narrator] It's estimated that 38,000 tons of aggregate

are necessary to construct one mile

of a four lane interstate highway.

[upbeat music]

Crushed rock, sand, and gravel, and lightweight aggregate

have been essential building materials since ancient times.

- From a historical perspective, you look back,

basically all of construction has been based

on using crushed stone, sand and gravel type products,

from the early Roman roads to today's interstates.

Basically our nation and our economy

are based on a solid foundation of construction aggregates.

- [Narrator] Unlike rock quarries,

where we rely on explosives to blast the aggregate loose,

[ground explodes]

the deposits in many sand and gravel quarries

come ready made by mother nature.

They're situated where the loose rock has existed

since prehistoric times,

like here in Prince George County, Virginia.

About a hundred million years ago,

a river ran through this area,

leaving layers of rock along its shores.

- Weathering breaks the rocks down

into various size fractions.

As they're moved along the river channels,

they are rounded and broken into smaller and smaller sizes.

- [Narrator] With each passing century.

The river deposited more and more layers

of loose sand and gravel.

- The excavator's loading material

that's not been blasted,

it's a loose material that we can dig quite easily.

- [Narrator] Sand is composed of rocks,

such as feldspar, limestone and quartz.

Gravel consists of pebbles, stones and fragments

of such minerals as shale and granite.

- We mine the sand and gravel

with a 5.6 yard cubic excavator.

Our haul truck's are 40 ton articulated trucks.

On a good day, we can average between eight and 10,000 tons

with this operation.

We haul the material to the surge pile,

dozer pushes it over,

and a loader picks it up and puts it into the feed hopper.

- [Narrator] The feed hopper distributes the sand and gravel

onto a huge conveyor belt

that transports it to the main processing plant.

- With the price of diesel fuel going up,

we didn't want to have to haul the material over a mile,

so we installed almost a mile of conveyor belt

that will carry approximately a thousand tons an hour.

- [Narrator] At the processing plant,

a vibrating machine with a series of sifting screens

separates the sand from the gravel.

- Once the material hits the number one screen,

that material is then sized

according to whether it goes into the gravel

or the sand circuit.

- [Narrator] Each of the screens has a smaller mesh

than the one above it.

The larger gravel rocks stay at the top,

and the smaller sand particles drop to the bottom.

- That begins a process of sorting the material by size.

It's essentially like this.

[sand pours]

[can rattling]

The material goes across the first screen,

and then goes through a series of additional screens

and is sorted by size in decreasing diameter.

- [Narrator] Once separated from the gravel,

the sand is sent through an additional screening process

in water filled classifying tanks.

Much like panning for gold,

the finer sand particles rise

to the top of the water separator,

and the heavier ones drop to the bottom.

- This is a finer sand that we pull out our core sand.

We then take this material,

let it go by gravity back down to the ground level,

pump it back up again, and resize it even further.

- [Narrator] After processing,

the sand and gravel are ready to be shipped.

The construction aggregate business is so competitive

that shipping costs are a major concern.

Therefore, most quarries are located

close to construction site areas.

- Construction aggregates are typically used

within 20 to 30 miles or their point of production.

- That is unless there are no local suppliers.

Then the material will have to be shipped longer distances.

In this case, a barge is the likely transport.

- This pit is adjacent to the Appomattox River,

we ship quite a bit of our material on barges

down to the Norfolk area.

Finished product is loaded on our barge load aid facility

here behind me.

Dump trucks dump it in a grizzly hopper

up the conveyor belt onto the barge.

This barge will hold approximately 2,000 tons.

[rock music]

- [Narrator] The aggregate is often shipped

to concrete plants,

and then sent off to make our churches, swimming pools,

and shopping malls.

Although rocks are most useful as building materials,

they may soon rock our world in a surprising new way.

In fact, we're starting to light up our cities

with an endless power source, not so deep beneath our feet.

The world is looking for sources of clean, reliable,

and renewable energy.

Northern California has found it.

- We're in the Mayacamas Mountains

of California's coast range

at the Geysers power plants.

The Geysers power plants are geothermal power plants

that cover 40 square miles of the mountains here

and generate enough electricity to provide 850,000

households with electric power.

- It's the largest geothermal area,

for it's producing power, in the world.

- [Narrator] And where does this geothermal energy come from?

Hot rocks.

In most places, molten rock or magma

exists very deep in the Earth,

where temperatures are extremely high.

The Geysers area is unique in that the magma

is very close to the Earth's surface.

- The heat that supplies the Geysers is supplied

from liquid magma about five miles deep,

this liquid magma that was left over

from a volcanic period that existed here

about 1.3 million years ago.

That volcanism is long since gone,

but it's left behind these pools of magma.

- [Narrator] In some of the geysers,

this heat bubbles right up to the surface.

- This is a steam vent, also known as a fumeral,

and it's evidence that we're very close

to a geothermal resource here.

Steam exits that vent at 250 degrees,

causing that water to boil.

If you fell in there, you could get boiled alive.

- [Narrator] The owners of the Calpine Corporation

operate most of the Geyser power plants,

but they aren't the first ones to take advantage

of this unique place.

- This area was known to the Indians thousands of years ago

when they lived here.

They utilized the hot Springs for hot steam

and for hot water.

Later on, in about 1847,

an Explorer named William Bell Elliot

happened on this area and was really quite surprised

to see steam venting out of the ground

and hot bubbling mud coming up.

And so he returned to his companions

exclaiming that he'd found the gates of hell.

- [Narrator] During the 1920s, several attempts were made

to tap the geothermal energy resources here

for electrical power.

But it wasn't until the 1950s

that drilling technology became advanced enough

to make the resource truly productive.

- As they started drilling thermal wells

deep into the Earth's core to capture the steam

and utilize it to generate power.

From there, in the sixties, the first plant was built.

And since then they've built up to 23 plants

that have operated up here in the Geysers

almost for 50 years.

- [Narrator] The wells at the Geysers don't have to reach

all the way down to the liquid magma,

but only to where the rocks are hot enough

and there is enough water to create a large supply of steam.

Nevertheless, many of the wells are drilled

over two miles into the ground

until they reach sandstone.

- The sandstone's been heated,

and it has water in that turned into steam.

But on top of that sandstone is what's called a cap rock.

And that cap rock holds all that heat and steam pressure

down in the rock.

We drill down through that cap rock and into what we call

a geothermal reservoir.

And that reservoir is highly fractured,

so there's cracks and fishers that allow that steam

to travel, essentially, through the rock

and then into our well, or pipe.

- [Narrator] The drilling equipment is identical

to that used for oil and gas wells.

- This kind of drilling that we're in right now,

we're in hard rock drilling, very deep.

We use these tungsten carbide bits here.

These are the cutting edges here.

It's very, very hard.

It wears very, very long time.

- Once drilled, the steam is channeled

into an intricate network of pipelines,

stretching over a hundred miles.

- This is a geothermal well head,

connected to a steam well

that extends two miles underground.

The steam exits this well head at 350 degrees Fahrenheit,

and the steam's transported down the pipeline

at 70 miles an hour to the power plant.

- [Narrator] The pipe itself originates from rock material,

primarily iron ore.

- Pipes made out of iron,

when an iron gets hot, it expands.

When the iron starts out cold, when it's first installed,

it might only be 35, 40 degrees here at the Geysers.

And this is 350 degrees right here,

so the pipe has to be allowed to expand and contract.

And that's why everything is mounted

on these little shoes like this.

It gives us some leeway, when it gets hot and cold,

to slide back and forth.

- [Narrator] The steam is piped to giant turbines.

[upbeat music]

This power is then transferred to a generator.

- That generator is generating 50 megawatts

of electricity right now, enough to power 50,000 homes.

- [Narrator] The electricity is then sent

all over Northern California.

Then it's time for the water to pay another visit

to the hot rocks.

- What you see behind me here

is the power plant cooling tower.

After the steam has expended its energy in the turbine,

it's condensed and sent out here to the cooling tower

to be cooled where it could be injected back into the ground

to produce more steam.

What you see coming out of the top of the cooling tower

is not smoke.

It's just pure water vapor that's being cooled

through evaporation.

- We have an endless supply of energy

in which we can generate power.

This is renewable energy that works around the clock.

The geothermal power comes up naturally 24 hours a day,

seven days a week.

- [Narrator] Across the globe, many countries

are looking to the heat of hot rocks

for future energy needs.

- The potential for geothermal energy is huge.

The Earth has an inexhaustible supply of energy.

Worldwide, geothermal energy is produced

in about 20 different countries.

- [Narrator] In the areas of the world where steam

isn't as close to the surface

as it is at the Geysers,

engineers are experimenting with a process

called hot dry rock technology.

- In hot dry rock geothermal technology,

there's no steam locked up in the hot rock

that exists down under the crust.

So what engineers have tried to do

is drill down into that rock,

and then, taking whatever water source

they happen to have available at the surface,

pump it down into a well,

let it work its way out into the cracks and fishers

in that hot, dry rock,

and then drill more wells around the perimeter,

and try to recover that water as steam

to produce electricity.

- [Narrator] The wills have to be deeper

with hot rock technology.

But theoretically, the process could produce enough energy

to supply the entire world's demands.

Not bad for a bunch of rocks.

Whether they're creating energy for our homes,

iron for our industries,

or concrete for our infrastructure.

Rocks partner with us in stony silence.

They've stood by us in the past,

and they will support our future.

Rock on.