ON AN island paradise off the north coast of Japan, there鈥檚 a volcano with
treasure seeping out of its pores. All this summer, Russian scientists will be
landing on Iturup Island with lengths of timber over their shoulders and a
glimmer in their eyes. They are on their way to build a wooden pyramid over
Kudriavy鈥檚 steaming vents, hoping to tap some of the volcano鈥檚 wealth before it
vanishes into thin air. They are on their way to bag some rhenium.
At $1450 a kilogram, rhenium is not your average element. An extremely
hard-wearing silvery metal, it is used in satellites, aeroplanes, high-tech
thermometers and tactical missiles, and it鈥檚 a handy catalyst for producing
high-octane fuels. Rhenium is also extremely rare鈥攈ence its hefty price
tag. And yet Kudriavy is full of it. That鈥檚 why researchers are now hunkering
down in the volcano鈥檚 crater, taking the first risky steps to turn the volcano
into an operational mine.
Kudriavy caught the world鈥檚 attention back in 1992 when Mikhail Korzhinsky
from the Institute of Experimental Mineralogy in Chernogolovka and his
colleagues stumbled on some strange rocks in the rubble of the volcano鈥檚 crater.
The soft, light-grey fragments, which everyone assumed were ordinary molybdenum
sulphide, turned out to be rhenium sulphide鈥攖he first known mineral of
rhenium unpolluted by other metals. It was dubbed rheniite, and contained an
amazing 77 per cent rhenium by weight.
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That means Kudriavy is enriching rhenium from its gases by about eight orders
of magnitude, carefully excluding all the other metals found in higher
abundances, and spitting out metallic chunks that have been described as
anything from 鈥渂eautiful鈥� to just plain 鈥渨eird鈥�. Why it should do this is still
anyone鈥檚 guess. Kudriavy is just one bump in a string of volcanic islands known
as the Kuril Archipelago, a geologically young and still active paradise. The
last time its summit crater erupted was back in 1883, though mild explosions
have happened since then and it still spits lava down its western side. At
present its summit holds a 300-metre crater spattered with about a dozen
fumarole fields, where the pent-up gases violently escape at temperatures up to
950 掳C, which is remarkably hot鈥攅ven for a volcano. It seems that only
a vent smack in the middle of the crater, spewing gases at 530 掳C, is
producing rheniite.
With the discovery of this rheniite in the early 1990s, Kudriavy started to
look like a treasure trove. And Korzhinsky鈥檚 colleague, Genrikh Steinberg from
Russia鈥檚 Institute of Volcanology and Geodynamics in Yuzhno-Sakhalinsk, was
getting ideas. 鈥淗e was talking about getting a dump truck and just carting the
stuff off,鈥� says Terry Adams, president of British metal mining company Adams
Metals of Guilford, which provides for about 65 per cent of the West鈥檚 rhenium
needs. And, he adds, that still might not be such a bad idea. There are probably
just 10 tonnes of the ore stocked in the volcano, says Adams, but 鈥渇or a small
dedicated operation that鈥檚 quite viable鈥�.
But the Russian researchers thought they could do better. If rhenium was
plopping out of the volcano as a mineral at the rate of several grams per day,
just how much was being belched out as a gas? Since Kudriavy is relatively
quiet, they had reason to be sceptical. Looking at sulphur dioxide emissions, a
common way of evaluating volcanic gas production, Kudriavy only puts out about
75 tonnes of SO2 a day, compared with 10 000 tonnes for hyperactive
volcanoes. But if the rhenium concentration were high enough, it might still be
worth tapping the gas.
So Tobias Fischer, assistant professor of volcanology at the University of
New Mexico in Albuquerque, went to Iturup with some of the Russian team in 1996
to measure the amount of rhenium in Kudriavy鈥檚 gases. They found up to 6
micrograms per litre of condensed gas鈥�10 times as much as the average
volcano.
So Steinberg, along with Alexander Kremenetsky and Felix Shaderman from the
Institute of Mineralogy, Geochemistry and Crystal Chemistry of Rare Earth
Elements in Moscow, devised a plan to swipe the island鈥檚 valuable gas. Their
invention (patent pending) involves fitting a cap over one of the volcano鈥檚
fumaroles. The gas spews into the cap and is funnelled through a
pipe鈥攈elped along by a small fan鈥攖o a chemical trap filled with an
absorbent natural rock called zeolite. This Swiss-cheese conglomerate of
aluminosilicate, doped with various positive ions, has many uses. For example,
zeolite is found in a lot of washing powders, where it extracts ions from the
water, making it softer and more effective for cleaning. You can also find it in
cat litter, where it absorbs moisture. And now you can find it on top of a
Russian volcano.
Tests show that natural zeolite can absorb the rhenium as a disulphide with
the same formula as the mysterious rheniite. All you have to do is heat the
zeolite, and volatile rhenium sulphide emerges, while more polar molecules such
as water remain behind. So, will the process yield enough rhenium to make it
worthwhile? Outsiders are curious, but not terribly confident. 鈥淚t sounds
far-fetched to me,鈥� says Rob Bell, a senior research fellow with the Royal
Institution of Great Britain, London, who works on computer modelling with
different forms of zeolite. 鈥淏ut not completely impossible.鈥�
This month, Kremenetsky鈥檚 team is setting up a test pyramid鈥攚ith a base
of 9 square metres鈥攐ver one of Kudriavy鈥檚 rhenium-enriched fumaroles, to
see if the plan will work. The pyramid is made of wood鈥攁nother risky
aspect of the scheme. Kirill Schmulovich, a geochemist from the Institute of
Experimental Mineralogy in Chernogolovka, who was with Steinberg when they
discovered rheniite, says his own experience on Kudriavy was not very
wood-friendly. 鈥淥nce, we put a stake in the soil, about one inch in diameter,鈥�
he remembers. 鈥淭he next year, no stake.鈥� Whether it burned up, was consumed by
acidic volcanic belches or was knocked over and buried by rubble, he doesn鈥檛
know. Whatever happened, it didn鈥檛 last.
Alexander Solov鈥檡ow, a colleague of Steinberg, objects to this criticism. He
says the Japanese had log structures on Kudriavy for years, and claims that
Schmulovich simply lost his stick. Still, the future has bigger, better, more
solid things in store. Kremenetsky plans eventually to cap Kudriavy鈥檚 fumarole
field鈥攃overing about 35 per cent of the crater鈥攚ith a huge concrete
or ceramic dome. Estimates of just how much rhenium they鈥檒l catch vary widely.
Fischer reckons that only 270 kilograms of gas are emitted a year. How much of
that could be caught he has no idea. But the Russian rhenium-hunters are placing
their bets an order of magnitude higher, estimating that they鈥檒l get 2 tonnes in
their traps each year. For comparison, about 45 tonnes of rhenium are produced
annually worldwide. The scaled-up operation, says Kremenetsky should give them
their money back by the second year.
Right now the world鈥檚 rhenium supply comes mainly from molybdenite, a
by-product of copper mining. The ores have to be roasted and the rhenium
extracted from the gas, which is a relatively time-consuming and expensive
process鈥攖he first gram of rhenium extracted by the German chemists Ida and
Walter Noddack in 1925 took a whopping 660 kilograms of molybdenite ore and cost
$15 000 to produce. Production methods have improved considerably since
then, and the concentration of rhenium in these ores is higher than in
Kudriavy鈥檚 volcanic gases. But if it proves cheaper and easier to get the
rhenium from this new source, then it could be just what the engineer
ordered.
鈥淚 can see five to ten years down the road there might be a real need to
recover the rhenium from that volcano,鈥� says Tom Millensifer of the Illinois
metals and minerals company Powmet, one of the bigger players in the American
rhenium market. 鈥淭he need for rhenium is growing, but the supplies aren鈥檛,鈥� he
explains. The amount of rhenium produced these days depends on the copper mines,
several of which have closed down in recent years. Meanwhile, demand for
鈥渟uperalloys鈥� is going up, primarily for use in aeroplane turbines, and rhenium
has become an essential component. Add a dash of rhenium to your metal recipe
and you get an alloy that has high strength at high temperatures, isn鈥檛 brittle,
can be easily hammered into shape, minimises friction in a system, and can be
recycled thousands of times. With the high-tech industry exploding, Millensifer
predicts that demand for rhenium could very well exceed the supply.
With such a buoyant market, other rhenium hunters have joined in the search
for volcanoes with valuable burps. Adams has had friends and colleagues looking
in Chile for another Kudriavy, but to no avail. If the Russians pull it off,
they may be the proud owners of the world鈥檚 one and only volcanic rhenium
mine.
Still, it won鈥檛 be easy. They鈥檒l have to ensure that their zeolites are not
clogged with chlorides and other metals, and somehow deal with the changing
landscape of an active volcano. While Kudriavy may not have erupted since 1883,
it still hiccups occasionally. Last year it blew a hole 30 metres across in the
mountain top. The team would like to put in a system of seismic monitors. In the
meantime, says Solov鈥檡ow, 鈥渨e hope for good luck鈥�.
Most experts in the metal-mining world laugh a little when you bring up the
prospect of stuffing a cap over Kudriavy鈥檚 head and sucking up the rhenium. Not
because it鈥檚 a bad idea. But with the rotten-egg stench of hydrogen sulphide
belching out along with the volcano鈥檚 treasure, at temperatures of up to
950掳C and at pressures high enough to make the belches roar and hiss, it
might not be all that much fun. Adams shakes his head over Steinberg鈥檚
dedication to the burping volcano. 鈥淗e鈥檚 spent most of his life up and down
those islands,鈥� he says. 鈥淩ather him than me.鈥�