(staccato synth music)
- [William] This is
sand under a microscope.
But, so is this, and this, and this.
Sand isn't one thing,
it's incredibly diverse.
And all its differences
have global significance.
We're on a sand scavenger hunt.
We're collecting samples
and we're gonna send them
to Cory in New York to
look at under a microscope.
And we're doing all this because sand
is actually one of the most critical
natural resources there is.
It has a million different uses,
but it's a crucial component of concrete
and humans use more concrete
than any other material besides water.
It's fueling these huge construction booms
in places like India,
China, and parts of the U.S.
And you might have seen news
about the world running out of sand.
That's true, but it's not that simple.
The future of construction
actually depends
on the science of each
tiny little grain of sand.
(car engine starts)
First off, the definition
of sand is really broad.
It can be made out of any
kind of rock or mineral.
Really, what makes sand sand is size.
Each grain is somewhere
between 0.05 millimeters
and two millimeters across.
Smaller than that, and it's silt,
larger, and it's gravel, that's kinda it.
But what sand is made
out of, where it's from,
what it's shaped like,
all of that is important
if you wanna build with it.
The basic recipe for
concrete is pretty simple.
Sand and other large rocks
get mixed together with water
and cement, which is a
powdered binding agent
commonly made from limestones and clays.
The cement solidifies with the sand
and rock particles to form concrete.
And what you really want
for concrete is river sand.
The grains are rounded and
their size is consistent.
That helps the sand bind with the cement.
It's also made with a nice
hard mineral like quartz
without too many softer minerals mixed in.
And river sand, really good river sand,
ticks all of those boxes
because of this incredible
journey it goes on.
- Think about the individual grain of sand
that was once on the mountaintop
- [William] That's Frank
Leith, a geology expert
at a sand producing company
called Vulcan Materials.
Basically, the sand in
the Sacramento River here
started up to 400 miles away,
around the Klamath mountains
of northern California.
Very slowly over time, little
jagged bits of those mountains
chipped off by freezing,
thawing, rain, wind,
- Fell down into the canyons
and then fell into the rivers.
In the rivers themselves,
once they're underwater
they're being transported and
bouncing against each other
hitting each other millions of
times or more, and impacting,
and knocking all the corners
off of that angular grain
of material that fell down.
- [William] Along the way, softer minerals
are slowly dissolving away
so that, after 400 miles,
you get this, what, in lots of situations,
is the ideal sand for concrete.
Of course, river sand ends
up somewhere too, the beach.
It's maybe the most
mature sand that there is
because once a river
deposits it on the beach,
it gets continually worked
and reworked by wave action.
But, beach sand comes with its own issues
It's salty, which can
mess with the chemistry
of the concrete mix, and it's less pure.
There are lots of shells
and bits of sea-life
and who knows what else.
That can make the concrete
softer, or chemically reactive.
You can fix both those things,
but the concrete might be
more expensive or trickier to work with.
So, that's beach sand.
(engine starts, light guitar music)
There's one other kind of sand
we wanted to compare, manufactured sand.
Which is, basically what it sounds like.
- Making small rocks out of big rocks.
- [William] Crushed sand is
trickier than natural sand
because it doesn't go through
that natural weathering process
so it's very sharp and angular.
But unlike river sand,
we don't have to wait
for mountains to weather
down over millions of years,
we can make it ourselves.
(cars driving by)
So we got some of that too.
They wouldn't let us
film inside the quarry
but they gave us a very large sample.
(car door opens)
(staccato synth notes)
River, and manufactured
sand are pretty different,
but they both solve the other
huge driver of sand scarcity.
Sand is cheap to produce
but bulky and heavy to ship.
Frank says transportation
of sand can cost them
two to four times more than production.
So, sand usually stays local.
- [Frank] You know, when you
see an average dump truck
that's driving down the road with material
it's probably not going
more than 30 or 50 miles
from the source of where
it got its material.
- [William] Any farther than that,
and it's probably not
worth the cost to move it.
Rivers are so useful because
they cover a lot of ground
and quarries can create in lots of places.
Both of them allow builders to
collect and use sand locally.
When you don't have ideal sand
nearby, scarcity gets scary.
And in the short term, that's what
'we're running out of sand' really means.
There just isn't enough sand
in the places we need it most.
That's where you get these
reports of sand mafias in India,
stealing entire riverbeds
to meet massive demand
or some construction projects in Dubai
that have resorted to shipping sand in
from place like Australia.
Dubai is surrounded by desert sand,
but it's actually too fine and smooth
to work well in concrete.
Again, you need the right sand
in the right place for the right job.
(staccato synth notes)
So, how'd we do?
Well, we sent the samples to Cory,
he got them all organized and imaged
and we saw a lot.
We called Frank back to get his take.
- [Frank] The manufactured
sand popped right out
I mean there's just corners
and angles everywhere
which really shows how fresh and young
that manufactured sand is
relative to the, to the
other sands that you sampled.
- [William] Frank saw a big contrast
between the manufactured sample,
and both the photos of
river sand that we sent him.
- [Frank] Both of them have
a very high concentration of,
of rounded quartz grains.
- [William] It's those
smooth quartz grains
that work so well in concrete.
As to the beach sand, the
grains were nice and round,
but there were more mystery
grains in there too.
Like this big blue-green
one in the middle.
- [Frank] One possibility
is, this is a tourmaline,
it's also found in some
of your heavier minerals.
- [William] All in all,
we did pretty well.
But of course, it's so
much more complicated.
In reality, each one of those
grains went on its own journey
so even within a single sample,
collected from one place,
there's a whole world of sand represented.
- [Frank] Uh, in geology
there's, there's never a,
there's never a perfect
story, it's always a,
there's always some
additional detective work
that has to be done.
- So listen, there's a whole
other part of the story
we didn't talk about, and that's
the environmental impact of doing
all of this sand harvesting,
all around the world.
That's real, we just didn't
have time to talk about it
in this video but hopefully
we'll cover that soon.
