By Sue Nelson
BBC Radio 4
Spruce Pine, a modest, charmingly low-key town in the Blue Ridge mountains of
North Carolina, is at the heart of a global billion-dollar industry.
Although this Mitchell County community calls itself the Mineral City, with
just 2,000 residents one could dispute the city status. But when it comes to
minerals, Spruce Pine has definitely undersold itself.
The jewellery shops, highlighting local emeralds, sapphires and amethysts, hint
at the riches. The mountains, however, contain something far more precious than
gemstones: they are a source of high-purity quartz.
This ultra-pure mineral is essential for building most of the world's silicon
chips - without which you wouldn't be reading this article.
Geologist Alex Glover, of Active Minerals International, drove me to a disused
mine to see this quartz for myself. Our jeep bumped across dried creek beds for
miles until we reached two cathedral-like caverns of rock at Hoot Owl mine.
The rocks contain feldspar, silvery flakes of mica, flashes of garnet and smoky
veins of quartz. "Fifty years ago men were throwing away the quartz," explained
Mr Glover.
It's the most valuable strategic square acreage on the planet
Ira Thomas Spruce Pine Gem Mine
"But now it's prized and quartz is the high value item. These are the only
places that this quartz is found on the planet."
Spruce Pine quartz is considered the best in the world and can sell for up to
$50,000 ( 30,000) a tonne.
It is made, like all quartz, of silicon and oxygen but the process of making a
computer chip does not rely on its silicon; that can be obtained from common
sand.
The clue to why quartz is needed is in the process of making a silicon wafer.
These wafers are CD-sized slices of silicon upon which the chips are then
etched with electronic circuitry.
Salami slicing
To make wafers, a seed crystal of silicon is heated to high temperatures in a
giant mixing bowl until the molten, silvery metal can be stretched slowly
upwards.
"It looks like a long cylinder, a bit like a salami," said Bob Carland,
director of the Minerals Research Laboratory at North Carolina State
University.
"As it comes out of this bowl, it all has one crystal and so everything is
aligned the same way. The metal cylinder is then laid down and cut with a
diamond saw into slices of salami - in this case it's slices of silicon
wafers."
For these wafers to be made into silicon chips, the mixing bowls or crucibles
must be as "clean" as possible.
"Any slight defect on the inside of that crucible will be transmitted and get
sliced up into the chips," Mr Carland said.
"The amount of impurities in that chip is incredibly important. People
producing these wafers will then have a lot of rejects so it's important that
the chemistry of that bowl is near perfect."
Spruce Pine's high-purity quartz fits this requirement. It not only gets used
for crucibles, but for benches and other instruments that produce the chips.
These chips are essential for today's modern world, but outside the industry,
few people are aware of its dependence on quartz.
Unimin, one of the main mining corporations in the area, prefers to remain
modest. It politely declines any interview, unwilling to reveal how it extracts
quartz from the mountains.
Seen from the air, the scale of the operation reveals itself. The quartz mines
are enormous, stretching down mountain faces in tiers of rock ending in pools
of white sand.
'Serious commodity'
It's a far cry from how the mountain folk made their living.
Sixty-eight-year-old Ira Thomas is a ninth-generation miner who used to dig up
aquamarines and prospect for mica as a child.
He now runs the Spruce Pine Gem Mine, a jewellery shop near the scenic Blue
Ridge Parkway, and is saddened by the loss of community among those who mine
for quartz in industrial quantities.
"We have these huge corporations that have come in and bought out the little
mom-and-pop operations," he said.
"These guys were just people like me that were lucky enough to lease a property
that had minable quantities of whatever was on it."
Native Americans first mined these mountains but it was the arrival of a
railroad in 1912 that gave later settlers the chance to exploit mica, feldspar
and quartz on a much larger scale.
Today, in Mitchell County, one in 15 people works within the mining industry.
"That quartz plant just two miles down the road," he added, "is guarded like
Fort Knox. That's a top-secret process. So we've got a serious commodity here."
He's right. The quartz plants are protected by security guards, gates and
cameras and no one from the mining companies is allowed to talk to outsiders.
Lowell Presnell, historian and author of Mines, Miners and Minerals of Western
North Carolina, isn't surprised.
"With the competition in the world today, they have to be really strict," Mr
Presnell said, "because if they let their secrets out, somebody else is going
to be doing this and they'll undercut their price."
There are also valuable jobs at stake. Since 2000, Mitchell County has lost a
third of its manufacturing base and unemployment is at 14%.
North Carolina may be famous for its mountain folk and bluegrass music, but the
mines are the only industry it has left.
So far, it is safe. Synthetic quartz is economically too expensive to take the
place of Spruce Pine's high-purity mineral.
"It's the most valuable strategic square acreage on the planet," Mr Thomas
said.
"Because the world runs on computers, we all know that now. And if we locked
the gates to Mitchell County they could not make any more computers."
Sue Nelson presents Chips with Everything on BBC Radio 4 at 9pm on Monday 3
August.