2019-05-01_Discover

22 DISCOVERMAGAZINE.COM

BY GEOFFREY GILLER

SHAPED BY ANCIENT WAVES

AND WIND

The geologic processes that created this

perfect sand likely took millions of years,

says Jay Zambito, an associate professor of

geology at Beloit College in Wisconsin and

formerly a geologist with the Wisconsin

Geological and Natural History Survey.

Half a billion years ago, when this sand

was forming, Wisconsin was quite differ-

ent, and in a very different part of the

globe. It was closer to the equator and was

more or less at the edge of an enormous

inland sea. The land was mostly desert,

Zambito says, so the sand at that ocean’s

edge cycled back and forth between the

waves and the desert winds. “It’s just going

back and forth over and over until the

sand grains are finally deposited,” he says.

Quartz is more chemically stable than

most other common minerals. So as ocean

waves, rain and wind broke down rocks to

smaller particles on Earth’s surface, most

of those minerals weathered away, leav-

ing just quartz sand behind. That constant

motion, says Zambito, also helped give the

Mining the

Minuscule

Pure, round and super strong: This is the

only sand down for a fracking job.

Descending a few dozen feet into the open pit mine, visi-

tors enter a monochromatic world that looks like a desert

planet from Star Wars. On all sides, walls of nearly pure quartz

sandstone rise up, the sparkly tan of raw cane sugar, layered with

bands of different shades. Loose sand sits in small piles at the base

of the cliffs; in the distance, larger piles are being loaded into huge

yellow dump trucks that can move 70 tons of the stuff at a time.

But they’re not digging for valuable ores or precious metals

buried beneath all this sand. This is a sand mine, and there are

dozens like it in western Wisconsin. This state, and others in the

Midwest, have some of the best sand in the world.

Sand has been mined here for over a century. It’s used for glass,

casting in foundries, even playgrounds and golf course sand

traps. But in the last 10 to 15 years, the industry has exploded

because this sand has specific characteristics. It’s pure — almost

entirely quartz, or silicon dioxide — and the particles are round.

This combination makes Wisconsin sand ideal for use in another

extractive industry: hydraulic fracturing, or fracking, in the quest

for natural gas and oil.

O«

They’re not

digging for

valuable

ores or

precious

metals

buried

beneath all

this sand.

This is a

sand mine.

TO

P:^ M

ICH

AE

L^ P

AR

SE

N/W

ISC

ON

SIN

GE

OL

OG

ICA

L^ A

ND

NA

TU

RA

L^ H

IST

OR

Y^ S

UR

VE

Y.^ IN

SE

T:^ J

AY^

ZA

MB

ITO

NOTES FROM EARTH

At a mine in northwestern Wisconsin (above),

heavy machinery harvests the white sand (left,

magnified) used for hydraulic fracturing.