>> Earth, a unique planet,
restless and dynamic.
Continents shift and clash,
volcanoes erupt,
glaciers grow and recede--
titanic forces that are
constantly at work,
leaving a trail
of geological mysteries behind.
This episode explores
the incredible journey of
one of the most indestructible
and valuable metals
on the planet--gold.
Created in outer space,
an immense explosion
blasted minute particles of gold
at 70 million miles per hour
into the rocks that form
our planet.
How tiny pieces of scattered
gold accumulate to form
massive deposits is one
of Earth's great mysteries.
To find the answer,
Geological detectives sift
Through ancient riverbeds,
Hunting for hidden treasures
Above and below ground
And investigating
Alien natural wonders,
Finding clues that will
Ultimately reveal
"How the Earth Was Made." S02x13 America's Gold Original Air Date on March 2, 2010
-- Sync, corrected by elderman -- -- for www.addic7ed.com --
>> Gold has mesmerized man
for thousands of years.
The oldest known precious metal,
it plays a powerful role in
almost every culture on Earth.
>> Since humans have been
on this planet,
gold has been prized.
It is such a unique mineral.
It is beautiful.
You can take an ounce of gold
and stretch it in a thin string,
and it'll go for 35 miles.
>> But the key to gold's
enduring value is its
inactivity. It won't bind with
anything else except itself.
>> Gold doesn't get used up.
It gets recycled.
The ring you're wearing
may be the exact same gold
that was in some of the gold
the pharaohs wore centuries ago.
With all these properties,
it's no wonder gold
has been treasured by man
down through history.
>> Man has mined gold
for thousands of years but found
only 160,000 tons worldwide,
enough to fit comfortably
inside a 4-bed house.
Physicists discovered
that this ultimate metal
was created in outer space long
before planet Earth existed.
Over 5 billion years ago,
gold and other heavy-metal atoms
formed in the maelstrom
of a supernova,
a giant dying star.
As it exploded, shock waves
blasted minute gold particles
across the universe
at 70 million miles per hour,
scattering them far and wide
throughout the early
Solar System. As this cloud
of rubble compacted together,
the gold became trapped
inside the rocks of the newly
forming planet Earth.
Widely dispersed and inactive,
to this day, most of the Earth's
gold remains as tiny, isolated
particles in the rocks.
>> It's ironic, but gold
is around us everywhere.
It's in the soil
in our backyards.
It's in these rocks here
in the riverbeds.
But the problem is
it's in very small amounts.
In these rocks, the gold may be
at one part per billion.
That's like finding just a grain
of sand in an olympic-sized
swimming pool.
>> Unusually large stashes
of gold are concentrated
in a handful of very special
places around the world.
The largest, in southern
Australia, China,
South Africa, Peru,
and the western United States.
It is the geologists' job to
find out where and why the Earth
accumulates gold in large enough
quantities to mine.
The first pioneers of gold
geology were not scientists,
but gold-hungry prospectors
who scrutinized the rocks.
Their story began
over 150 years ago by accident.
In 1848, in the small
Californian town of Coloma,
along the American River,
James Marshall was digging
a trench for a water wheel
to power his lumber mill when he
made an extraordinary discovery.
>> He was digging it down
during the day and then using
water at night to flush out
the sand and gravel,
and he looked, and there
on the bedrock were
a couple of gold nuggets.
>> Rumors of California's
River gold spread like wildfire.
By 1849, over 90,000 people
from around the world
descended on the state.
Nicknamed the Forty-Niners,
these early investigators
searched the streams
in a bid to find their fortune.
Their first challenge
was to figure out where gold
accumulates in the river.
And they quickly discovered
that gold wasn't just strewn
anywhere along its course.
>> A clue to where the gold
would be concentrated is
black sand in areas like this.
You take a sample
and pan it out.
>> The Forty-Niners soon learned
if they found heavy black sand
in their pan, they were
onto a winner.
>> The process of panning
is a simple one.
You're really trying
to separate light materials
from heavy material.
>> In this sluggish water,
the heavy particles sink
to the bottom of the pan.
>> And you repeat the process
of washing away light materials
and then concentrating
the heavies on the bottom
until you get down
to just the black sand
and hopefully some nice gold,
even a small nugget like that.
>> IIn the same way,
rivers and streams
separate the heavy particles
from the light.
The gold and black sand
are flushed downstream,
but as they hit the sluggish
water on the inner bend,
they drop out of the flow.
And it's here in the sandbanks
on the inside bends of the river
that the Forty-Niners discovered
an absolute fortune.
In total, over 20 million ounces
of river gold were discovered
in the waterways of California.
But when they investigated
the valley sides above
the river, the Forty-Niners
discovered an even bigger
stash of gold.
>> And they wondered,
what was the deal with these
gold deposits that were up
and away from the water?
They took a close look at them,
and they could see that
these boulders were round
and smooth.
>> These rounded boulders
are identical to those found
in the rivers nearby.
>> And the reason is because
it's an ancient riverbed.
It's been left high and dry
by the flow of the river.
The river cuts downward and
leaves these deposits behind.
The miners continued to explore,
and they found some just above
the river like this,
but they found others tens
and even hundreds,
even a thousand feet
above the modern stream.
>> Using powerful water jets,
the Forty-Niners blasted
and flushed out a further
50 million ounces
of ancient river gold
from California's hills,
which still bear the scars
over 150 years later.
Similar river gold deposits
have formed all over the world,
including the greatest
treasure-trove ever found--
Witwatersrand in South Africa.
Its discovery in 1886 caused
another massive gold rush.
But this river gold is not found
on the surface.
Miners must descend over 2 miles
down the deepest mine shaft
on Earth.
>> Half the gold on this planet
has been produced from that one
group of deposits.
Most geologists believe
that these unique deposits
formed from ancient river
systems, concentrating these
in old river gravels.
>> Over millions of years,
thousands of ancient rivers
carrying gold spilled
into a huge lake, dumping
a massive gold deposit.
This ancient lake bed is now
buried miles underground.
To date, Witwatersrand
has produced over 1.4 billion
ounces of gold,
worth over $1.5 trillion.
And geologists believe
the same value of gold
still remains untouched.
In the search for California's
River gold, Forty-Niners found
heavy black sand, a sign
that gold is deposited
on the inside bend of a river,
and gold buried beneath rounded
boulders in the valley walls,
proof that rivers have been
depositing gold for millions
of years. The Forty-Niners
suspected that rivers were
carrying gold down from a source
somewhere in the mountain,
the mother lode.
but the quest to understand
where this mother lode gold
originated would take geologists
deep inside the Earth
and face to face with some
of the most destructive powers
on the planet.
>> In the 19th century,
the Forty-Niners plucked
70 million ounces of river gold
from California's streams
and ancient riverbeds,
valued at more than $80 billion.
But this easy gold didn't last.
The race was on to find
the source of the river gold,
the mother lode, and they
set off into the mountains
to investigate.
>> And this is what
the old-timers were
really looking for--
A big wide vein of quartz
filled with gold.
It runs literally for miles
through the countryside.
They were able to mine
millions of ounces of gold
from sources just like this.
>> With the discovery
of mother lode gold,
prospecting changed from
a solo quest to big business.
Hundreds of mines sprung up
all over California,
employing thousands of men.
Discovering what geological
force had concentrated gold
in California's mountains was
a puzzle that would bamboozle
scientists for decades.
In 1853, the Alleghany mine
opened in Sierra County,
California. Today, it's over
3,300 feet deep with over
40 miles of tunnels,
all leading to one special
slice of rock in the mountain.
>> Here I am, in the middle
of the mother lode vein.
It must be about 40 feet thick,
and it goes down half a mile
into the Earth.
This is the gold-bearing
quartz vein that the miners
were seeking.
>> Quartz forms from a liquid,
and as it solidifies,
it somehow traps lumps of gold
inside it.
>> It is loaded with gold.
If we break these quartz veins
open, though, we can see...
perhaps small amounts of gold
within the quartz.
This is just an amazing
piece of quartz. You can see
all the free gold in it.
It's just bright and glistens.
There are actually clues
to how the gold got here
within the quartz that was
deposited with the gold.
>> Trapped inside the quartz
are tiny bubbles of fluid.
They are minute remnants of
a stream of water and minerals
that once gushed up this vein.
Analysis of these fluid bubbles
has revealed the extreme
conditions that created
the gold seam.
>> That gold was deposited
at 600 degrees fahrenheit.
It was a very, very hot fluid
that brought the gold
and the quartz to this location
and deposited the vein.
>> But it was a mystery.
What was the driving force
creating all this hot fluid
which carried the gold?
In an old quarry nearby
lies a clue.
The gold-bearing quartz vein,
here stained brown,
is flanked by strange beds
of altered rock.
When the old-timers saw rocks
like this they would get excited.
They knew they were getting close
to the source of the gold.
They would see these rocks
had changed their color.
And then they would get
to the big mother lode quartz vein.
The source of most of the gold ore.
This quartz vein is sandwiched
between these altered rocks.
And looking at these altered
rocks, you see they're
all deformed. They're up on end.
They're sheared up.
They're broken. They're folded.
>> These veins run for hundreds
of miles in a north-south
direction. Similar sandwiches
of gold quartz and broken rock
are found along the entire
length of California,
and strangely, they all run
parallel to the coast.
Whatever immense force
shattered these rocks
must also have created
the hot fluid which carried
and concentrated the gold.
But what was it?
Geologists finally solved
the mystery in the 1950's,
when the revolutionary theory
of plate tectonics shed light
upon how California
and its mountains were made.
They discovered that beneath
the Pacific Ocean, a giant plate
of the Earth's crust moved
eastwards. It plowed into
the American continent,
crumbling huge slabs
of the sea floor as it went.
>> If this big rock
is ancient North America,
over the last 300 million years,
we had a spreading ocean floor
push the ocean and sediments
on top of the ocean
against North America
and stack these pieces
of ocean floor and sediments
on ocean floor up on end
against western North America.
>> California was pushed
above the waves, a mountainous
mass of crushed, crumpled,
and upended rocks separated
by huge cracks running deep
into the crust, creating
a landscape compiled of giant
slabs stacked parallel
to the coast.
This immense mountain-building
process also had the power
to create a piping-hot fluid.
Buried rocks were squashed
under unbearable pressure.
They superheated,
and a 600-degree fluid
was squeezed from them.
Like water running in a river,
this piping-hot fluid
had the ability to concentrate
the scattered gold.
As it washed through the rock,
it leached out minute particles
of gold, creating
a mineral-rich soup.
It poured into the giant cracks,
which pipelined it
to the surface.
As the fluid cooled,
the gold coagulated,
and the quartz crystallized,
forming a solid
gold-bearing quartz vein.
In total, 35 million ounces
of this mountain gold
were blasted out of California,
one of the most profitable
gold-mining areas of its time.
>> Wherever you have oceanic
plates colliding with the edge
of a continent, you're always
going to create fluid,
you're always going to move
those trace amounts of gold,
and that will get focused
into major faults to form
large lode gold deposits.
They're part of
the mountain-building process.
>> Similar gold-bearing quartz
veins lie beneath the coastal
mountains all around
the Pacific rim, where the ocean
floor has crumpled under
gigantic Earth forces.
Scientists investigating
how California's mountain gold
formed have found...
Ancient fluid bubbles,
proof that a hot liquid
deposited the quartz and gold;
Parallel beds of broken,
altered rock, evidence
that the gold-rich fluid
was squeezed from rocks
as mountains formed.
By the 1880's, only 30 years
after the first gold strike,
California's mountain gold
became increasingly difficult
to find. By then, gold hunters
in neighboring Nevada
had stumbled upon an entirely
different type of gold deposit,
but it was the sort of deposit
that could drive men to murder.
>> In the 19th century,
Forty-Niners found
70 million ounces of river gold.
Then they began to ransack
the mother lode, blasting out
over 35 million ounces
of mountain gold,
squeezed from the rocks
as California formed.
[explosion]
For many years, scientists
believed that only the colossal
forces that created mountains
had the power to concentrate
gold scattered throughout
the rocks. But gold strikes
made in neighboring Nevada
were to shatter this theory.
Massive gold veins were found
in the Sagebrush Hills
of the desert. A tidal wave
of gold hunters left California
heading east. The almost
uncharted desolate state
of Nevada began to light up
with life, as gold strikes were
made across the high desert.
This was the gunslinging
Wild West, and the rough
mining town of Bodie had one
of the toughest reputations.
>> It's hard to imagine
more than 8,500 people
up along this stretch here,
lawlessness, lots of fights
breaking out.
[gunshots]
Lots of saloons, opium dens,
and brothels.
>> It was said that a man a day
was killed in Bodie.
[gunshot]
And some historians believe
the fickle geology
of these gold deposits
may have played a part
in this murder rate.
>> Here, the veins were much
more segmented and broken up.
So while one miner
might be mining along
on the vein, another miner
might not be, which would lead
to animosity and tension
and the occasional fight.
>> Geologists realize that,
unlike California's gold seams,
which ran parallel to the coast,
Nevada's were scattered
randomly across the desert.
The hunt was on to understand
why Nevada's gold veins
were so chaotic.
300 miles northeast
of the cramped old mine in Bodie
is the Midas mine.
Large enough to drive
a truck down, it's one
of a handful of remaining
gold quartz mines in Nevada,
and it's a geologist's paradise.
>> It's wonderful to have
an underground mine, because
when you go underground,
you have a 3-dimensional picture
of the geology.
It really helps you get
a feel for what clues
to be looking at that we
might see on the surface
that we might see
better expressed underground.
>> Working mines like Midas have
become geological laboratories
and are helping to unlock
the mystery of Nevada's
scattered gold veins.
Every day, the miners drill
the face and pack it
with explosives, exposing
new networks of quartz veins.
This is just like the old days
but we're high-tech.
They're gonna drill a space out.
Will load it with explosives
and blow it up.
>> 450 pounds of explosives
are about to blow to reveal
the gold-bearing quartz vein.
[explosion]
>> That was great, and to think,
it's so much safer than what the
old-timers had to go through.
>> Once the dust settles,
it's possible to take
a closer look.
>> This is quite a nice big
quartz vein. If I compare
these quartz veins to the veins
that I've seen in California,
they're substantially different.
For one, if I look at these
bands, these dark gray bands
in here.
>> These gray bands are
the first sign that something
very strange has happened here.
>> In a hand sample,
I'll see that there's
lots of gray material.
All that gray material
is silver.
If I look even closer,
I can see little fine flecks
of yellow. That's gold.
The source rock that formed
all of these veins
was much different
than the source rock that caused
the California veins to form.
The California veins
only have gold, and these
are loaded with silver.
>> And the clue to the identity
of the source of Nevada's gold
lies either side
of the quartz vein.
Unlike California, these
wall rocks are not crushed
and have never been
on the ocean floor.
>> This wall rock is
of a volcanic origin,
very similar to, like,
Mount St. Helen's.
>> So it wasn't
mountain-building
that concentrated the gold
and silver in this vein.
It was a volcanic process.
Perhaps the Midas mine
was once a giant volcano.
Geologists went looking
for clues not inside the mine,
but directly above it.
>> Everywhere above
the Midas mine, we see
these strange outcrops.
They're flat on the top
like a table, and if I look
closer, I can see fine
little bands and layers.
>> The outcrop is made of thin
layers less than 1/8" thick.
And there are thousands
stacked on top of each other
like a deck of cards.
>> You've got browns and
yellows, whites, and purples.
Understanding outcrops like this
will help us understand why gold
is deposited at such shallow
depths within the Midas mine.
>> These distinctive
layered rocks are not formed
by a volcano, but another type
of volcanic process that can
still be seen today in Gerlach,
northwest Nevada.
In the middle of the dry
blackrock desert, they found
a mysterious oasis,
and rising out of the landscape
a spectacular multicolored
hot spring, one of over 300
in Nevada.
This bizarre geological wonder
began to form just 45 years ago.
>> Volcanic processes beneath
the Earth heat the groundwater.
It spills out at the surface,
and like a boiling teakettle,
dumps a layer of mineral scale.
>> The water is slowly running
over the tops of these terraces.
It's depositing minerals
in fine little sheets,
kind of like a deck of cards
or a book on end.
This rock, from over there,
has fine laminations or layers.
Rocks like these and terraces
like those are found right above
the Midas mine, which tells me
that Midas was once
an enormous hot spring.
>> Geologists realized it was
hot springs that brought
the gold and silver quartz veins
to the surface in Nevada.
Gold and silver particles
are scattered in molten rocks
deep inside the Earth.
This hot rock released
a gold and silver rich fluid.
As rainwater soaked into
the ground, it reached
the scorching rocks deep
in the crust and superheated
to 900 degrees fahrenheit.
Hot and buoyant, the water began
to rise, sucking up the gold
and silver soup as it went.
As it neared the surface,
the water boiled and dumped
bands of silver and flecks
of gold in the chaotic fractured
pipework of the hot spring.
>> Imagine this landscape
15 million years ago--volcanoes
as far as the eye could see,
hot springs dotting
the landscape here and there.
>> Gold is forming at this
moment in hot springs
all over the world.
Even Yellowstone has traces
of gold in its water.
One of the world's biggest
and most profitable gold mines,
Yanacocha, northern Peru,
is a gold and silver deposit
which man has plundered
since the rule of the Inca
800 years ago.
High in the volcanic Andes,
it's a massive 535 square miles
and has produced over $5 billion
worth of gold, all of it
originating beneath
a bubbling hot spring.
Scientists investigating
how gold-silver veins
formed in Nevada
have found volcanic wall rock,
proof that the gold-rich fluid
came from molten rock,
and a multicolored layered
outcrop, evidence that ancient
hot springs deposited gold
in Nevada.
Nevada's hot-spring gold
deposits yielded over 40 million
ounces of gold and 500 million
ounces of silver, but by 1920,
Nevada's gold seams were
increasingly uneconomical
to mine. The desert became
littered with ghost towns.
It looked like America
had run out of gold.
But in 1961, a new type
of deposit was found.
But it couldn't be seen
or touched. It was invisible.
It would become the biggest
strike in the history
of America's gold.
>> America's gold was
concentrated by incredible
mountain-building forces
that formed California...
and volcanic processes deep
beneath Nevada's hot springs.
But as the deposits
became exhausted,
geologists frantically searched
for new stashes of gold.
Then in 1961, geologist and
gold prospector John Livermore
noticed a suspicious
50-mile-long crack
in the middle of Nevada
called the Carlin Trend
and set out to investigate.
>> John Livermore came to these
hills following up a theory
that gold deposits would be
aligned directly above a deep
crack in the Earth's crust.
He'd come up to outcrops
like this, and he would go ahead
and want to look at them.
>> The rocks are a strange
mixture of mud and quartz,
a mineral created in hot fluid
and a good clue that gold
might be deposited nearby.
>> Based on his experience,
he knew a lot of hot fluid
had come up this crack.
However, he couldn't see
any evidence of gold,
no quartz veins,
no visible gold.
But on a hunch,
he sampled this rock,
took it back to the assay lab
to see if there was
any gold in it.
>> In assay labs,
rocks are crushed
and blasted in a furnace
to over 1,800 degrees.
And as the liquid rock cools,
the minerals begin to separate.
>> At the end of this process,
something extraordinary
has happened.
An ordinary-looking rock
actually contained a grain
of gold at a concentration
of about 5,000 times you would
normally see in the Earth.
It doesn't look like much,
but this is what they mine
every day.
>> Livermore's hunch paid off.
50 miles long and 5 miles wide,
the Carlin Trend is now one
of the largest mining districts
in the world.
This vast man-made pit is big
enough to be seen from space.
>> This is the BetzePpost pit,
one of the world's
largest gold mines.
It contains 45 million ounces
of gold. They have to mine
10 tons of rock in order
to get one ounce out.
As you can see, it's huge--
2 miles long, a mile wide,
2,000 feet deep.
>> Because gold is so valuable,
the extraction of just a few
thousand ounces a day pays
for this extraordinary
mining operation.
And removing the gold ore
requires drastic action.
[explosion]
>> Wow. That's what 400,000
pounds of explosives looks like.
>> Giant diggers work 24 hours
a day excavating over
90 million tons of rock a year,
Enough to cover Central Park
in 55 feet of rubble.
But within this raw gold ore,
not a speck of gold has ever
been seen with the naked eye.
>> The mystery is,
where's the gold?
You can't see it.
The rocks look really ordinary.
The clue to where this gold
is hidden is in the internal
structure of this rock.
>> Magnified 500 times,
the gold is still invisible.
But this rock is
an extraordinary lattice
of quartz and mud perforated
with strange cavities.
>> It looks like a honeycomb,
like something's eaten away
at it. Clearly some strange
geologic process has
concentrated and hidden
the gold in the rock.
>> Scientists realized if they
were going to solve the puzzle
of how gold came to be hiding
in these rocks, first they
would have to understand
where the rocks came from.
A clue was found
in the 19th century by
cattle rancher Absalom Lehman
in the eastern reaches
of Nevada.
>> In 1885, Absalom Lehman
stumbled upon a hole
in the ground, and with rope
and lantern, he lowered himself
in the Earth and discovered
this beautiful cave system
with some of the most
spectacular cave formations
in the world.
>> The solid foundations
of this cave are made
of a messy mixture of mud
and calcium carbonate shells.
They are the remains
of tiny sea creatures,
evidence that Nevada
was once covered
by an ancient tropical sea.
>> For millions and millions
of years, creatures with shells
composed of calcium carbonate
began to rain down through
the ocean and accumulate
on the sea floor forming
this calcareous ooze.
Later, this ooze hardened
into a sedimentary rock
called limestone.
>> These extraordinary
structures in the cave
were formed when water eroded
the huge limestone bed
that sits underneath Nevada.
And back over at the Carlin
Trend, scientists noticed
that the gold ore was made
of a very similar type of rock.
They figured out that
the Lehman Cave limestone
and Carlin Trend gold ore must
once have been the same rock.
>> This is fresh limestone.
This is gold ore.
Clearly something happened
to change this rock into
this spongy gold-bearing ore.
Well, the clue is
in the chemical reactivity
of this limestone.
If I put dilute hydrochloric
acid on this limestone,
note how it fizzes.
Very reactive.
The acid is eating away
at the rock.
Now if I put the acid
on the spongy gold ore...
no reaction. The fluid
is soaking into the rock
like a sponge.
>> Scientists concluded
the reason Carlin Trend gold ore
did not fizz is that
it had already been attacked
by an acid.
Beneath the bed of limestone
at Carlin is a gigantic
vertical crack.
Geologists now believe
that a blast of hot, acidic
gold-rich fluid was once
forced upwards from deep
within the Earth.
It streamed through the crack,
drenching the limestone.
The acid ate into it,
leaving a spongelike
muddy framework behind.
And in the cavities, it dumped
quartz and the most minute
sprinklings of gold.
>> It's only been very recently
that scientists have been able
to use even more sophisticated
imaging equipment--microscopy--
to image down to the scale
of individual atoms.
>> Magnified 100,000 times,
tiny specks of submicroscopic
gold can be seen embedded
in the rock.
Zooming in further
a staggering 4 million times,
the gold particle
Is finally revealed.
This fleck of gold is only
5 nanometers in diameter,
one-millionth the size
of a pinhead, and each tiny
white dot is an individual
gold atom.
>> These ordinary-looking rocks
have produced 65 million ounces
of gold from a single crack
in the Earth known as
the Carlin Trend, and it's made
the United States the fourth
largest gold producer
in the world.
>> Scientists investigating
how Nevada's gold ore formed
have found a spongelike
rock structure, suggesting
that something ate away
at the limestone,
and gold ore not reacting
with acid, evidence that
an acidic fluid had already
attacked the limestone,
showering it with minute
particles of gold.
Similar Carlin type deposits
have since been discovered
yielding a further
35 million ounces of gold.
Yet these discoveries
may only be the tip of the iceberg.
Geologists are now using
state-of-the-art equipment,
hoping to unlock millions
of ounces of American gold
trapped deep beneath
the Nevada desert.
>> Throughout world history,
over 5 billion ounces of gold
have been recovered by man,
and almost 1/10th of this
has been found in California
and Nevada, adding up
to a staggering $280 billion
worth of bounty.
>> How much remains
is anyone's guess.
There is no reason not to
assume as much gold exists
as has been mined in the past.
But geologists, prospectors,
explorationists have found
the easy gold.
>> In the past, prospectors
and geologists homed in
on this easy gold by following
geological clues exposed
on the surface.
But vast areas of Nevada
are covered in a deep layer
of mud and gravel that has been
eroded from the surrounding
mountains. Geologists believe
hoards of gold still lie
concealed beneath this layer
of gravel, unseen by anyone
for millions of years.
Finding all this buried gold
in an area covering
110,000 square miles
is no easy task.
But one man has the ability
to see under the ground,
using pioneering technology.
>> I've got gold in the hills
around me.
I've got good reason to believe
that there's gold beneath me
in the rocks, if I could just
see through this sand
and gravel.
This little piece of equipment,
I believe, is going to help me
figure that out.
[machinery whirring]
>> The geo-probe is drilling
not for rocks,
but for groundwater,
200 feet below the surface,
and it's this groundwater
that holds the key to finding
Nevada's hidden gold.
>> If there's a gold deposit
concealed by the sand
and gravel, the groundwater
will interact with it,
and you'll pick up clues.
>> Traces of metals associated
with gold seep into
the groundwater, clues that will
lead Hodges to the secret
location of the gold deposit
deep below the surface.
>> Imagine an iron bar rusting
in a bucket of water.
The trace metals are going to
come out of that rusted iron bar
and are going to be disseminated
in the groundwater, and you
would be able to sample
that groundwater and tell
that there was an iron bar
somewhere nearby, just as we're
going to be able to sample
this groundwater and know that
there's a gold deposit
somewhere nearby.
So in a sense, it's like
the deposit of gold
is creating a scent.
>> If Hodges can latch on
to a whiff of this scent,
he can track it back
to find the gold.
Once the drill
is deep enough, Hodges
pumps out the groundwater.
[pump whirring]
>> Ok. I think I've got
enough sample now.
Somewhere in this bucket
of muddy water, I believe
we've got some clues.
>> This is no ordinary
pickup truck.
It's a state-of-the-art
mobile laboratory.
Hodges measures how many
trace metals are in
the groundwater,
and the scent here
is particularly strong.
>> And it's telling me
that I've likely got
a lot more trace metals.
Arsenic, antimony, mercury,
copper, lead, zinc are the kinds
of trace metals that are often
associated with gold deposits.
And it looks to me like we're
moving in the right direction.
>> In the same way
the old-timers traced the gold
up into the mountains,
Hodges tracks the increasing
concentration of trace metals
in the groundwater.
>> It's like a little childhood
game of hide-and-go-seek.
Am I getting hotter,
or am I getting colder?
And that makes it a science.
>> The net is tightening
around the gold deposit.
The scent is strongest in this
4-square-mile target zone.
But it's still too large an area
to begin test-drilling for gold.
To focus in further,
Hodges needs to literally
see inside the Earth.
>> Well, this instrument here
is a gravitometer,
and it has the ability
to measure how dense the rocks
are beneath this point.
Just as there's a landscape
here on the horizon behind me,
there's a landscape
in the bedrock underneath me.
>> Multiple readings
from the gravitometer
create a secret treasure map
of the terrain submerged
beneath the surface gravel.
From this rock density map,
Hodges can pinpoint the likely
location of the gold deposit.
He has found a suspect gas
in the Earth over a mile long
and 250 feet below the surface.
It's a good sign, as gold
is often found deposited
in deep cracks. It's time
to start drilling for gold.
The diamond-studded drill
probes the crack and extracts
a cylinder of bedrock.
This is the first
in a sequence of test drills
along the crack, and the results
are tantalizing.
>> After all this traveling
around, I'm finally able to see
the rocks for the first time.
These rocks have been
out of view for millions
of years, and to me,
it's one of the most exciting
things about this line of work.
I get to look at these rocks
before anybody else has ever
seen them, and I could compare
them with the rocks that I've
seen elsewhere in the mountains.
In this piece of core,
I see several different kinds
of fragments of rocks.
Some of them are quartz.
Quartz we know is good for gold.
>> Hodges could be on the verge
of a massive gold strike,
adding to his tally
of 30 million ounces
discovered so far.
>> Reaching down into the Earth,
pulling out a sample that says
there's gold in it and realizing
that you've done it.
And in a sense, it connects you
with those old-timers,
the same spirit of the old west.
It's exciting.
>> It's pioneering geologists
like Hodges who will find
what's left of America's gold.
Scientists and prospectors
investigating how gold
is concentrated around the world
have found gold in heavy black
sands, evidence that rivers
concentrate gold on the inside
bends...
Parallel beds of broken,
altered rock, proof that
gold-rich fluid was squeezed
from California's mountains...
Multicolored layered outcrops
show that ancient hot springs
deposited gold quartz veins
in Nevada...
And spongy gold ore,
evidence that an acid dumped
minute sprinklings of gold
in the rock.
The Earth does not relinquish
her gold treasure easily.
Man's irresistible urge to find
gold is the driving force
which helped pioneer
the science of geology.
Investigating how gold is
concentrated across the world
is not just the story
of metal and mining...
It's an epic tale that has
revealed how the Earth is
dynamically changing to this day.
And over billions of years
of the planet's history.
Living proof that the Earth
is never at rest.
-- Sync, corrected by elderman -- -- for www.addic7ed.com --