(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.