Vanadium is a metal, and by far its greatest use is in steel
alloys, where tiny amounts of vanadium improve steel’s hardness, toughness, and
wear resistance, especially at extreme temperatures. As I reported in my book
What Things Are Made Of, more than 650 tons of vanadium was alloyed with iron
to make the steel in the Alaska Pipeline, and there’s no good substitute for
vanadium in strong titanium alloys used in jet planes and other aerospace
applications.
Vanadium isn’t exactly one of the well-known elements, but
in terms of abundance in the earth’s crust, most estimates indicate that
there’s more vanadium than copper, lead, or tin. But it’s difficult to isolate,
and it wasn’t produced chemically as a chloride until 1830, when Swedish
chemist Nils Sefström named it for the Norse goddess of beauty, Vanadis,
perhaps better known as Freyja. It wasn’t until 1867 that pure vanadium metal
was isolated by British chemist Henry Roscoe, whose work on vanadium won him
the name of the vanadium mica roscoelite.
As a mineral collector, I’m attracted to vanadinite, lead
vanadate, because it forms beautiful hexagonal crystals, often bright red and
so abundant from one lead-mining area of Morocco that excellent specimens can
be had without mortgaging your house. Some vanadinite crystals are like perfect
little hexagonal barrels, and others can form needle-like spikes around a
central crystal, making the whole thing look like a cactus with caramel-orange
spines.
Some of the vanadium for making steel alloys comes from
primary mined vanadinite, but much more was once produced as a by-product of
phosphorous manufacture, because it’s commonly associated with phosphate rock. And
today, a lot of the world’s vanadium comes from refining crude oil and from fly
ash residues, which are products of coal combustion. I got curious about why
vanadium metal is so closely connected with these organic deposits.
Crude oil actually has lots of trace elements in it,
including metals like gold, tin, and lead, but by far the most abundant are nickel
and vanadium, as much as 200 parts per million nickel and 2000 parts per
million vanadium in some crude oils, especially heavy, tarry oils like those
found in Venezuela. In some oil, the nickel and vanadium can add up to 1% by
weight of the oil, an incredibly huge amount. Refining Venezuelan crude gave
the U.S. a lot of vanadium back in the late 20th century. But why is
it in there?
Oil and coal are both the result of decaying and chemically
changing plant matter. Forget dinosaurs; virtually all oil, natural gas, and
coal comes from plants – usually marine algae for oil and gas and more woody,
land-based vegetation for coal. There’s a class of organic molecules called
porphyrins. I’m no organic chemist, but these complex hydrocarbon molecules, made
of carbon, hydrogen, oxygen, and nitrogen have boxy ring-like structures with
open space in the centers. Chlorophyll and hemoglobin are related chemicals,
both of which contain metals in the middle of the structure, magnesium in
chlorophyll and iron in hemoglobin. The vacant holes in the centers of
porphyrins in crude oil are ideal for trapping metal molecules, and apparently
vanadium, in the form of a VO2 ion, is one of the easiest to trap because of
its molecular size and electronic valence.
The vanadium comes from the original oil source rock, so
there’s quite a range in vanadium content around the world. Heavy oils, like
the tars in Venezuela, hold more than fluid oils like those in Saudi Arabia.
This has more or less been known since at least the 1920s, and today the
vanadium and other metal contents of oils are being used to characterize the
original source rocks even when those source rocks no longer exist or are no
longer what they once were.
The United States has had no mine production of vanadium since
2013 and even then we were 94% dependent on imports. Today 100% of our vanadium
is imported, and we also produce some vanadium from imported crude oil and ash.
More than 90% of the world’s vanadium is mined in China, Russia, and South
Africa, although the US imports much of what it needs from the Czech Republic
and Canada as well as Russia. We also imported enough ash and refining residues
to account for 9000 tons of vanadium in 2015, mostly going as I said to making
steel alloys. A new emerging use is in high-capacity storage batteries, where
vanadium compounds make the electrolyte. These batteries have potential uses
for renewable energies such as wind and solar power, and although in 2015 and
2016 several companies were working on prototype designs, they’re still pretty
expensive batteries.
Even more exciting for me are some tiny, millimeter-sized
red-orange crystals in the specimens I found at the Mayflower Mine. All I knew
for a long time was that I couldn’t figure out what they were. By looking at
their crystal shapes and properties, I narrowed it down to two very strange and
very rare minerals – gottlobite, a calcium-magnesium vanadate, and calderónite, a lead-iron vanadate. Both
of these minerals are so obscure I didn’t really seriously imagine I had
actually collected one of them. But, thanks to an analysis by Stan Korzeb, the
economic geologist at the Montana Bureau of Mines and Geology, it turned out
that I did indeed find calderónite,
32 years before it was described as a new mineral in 2003. Stan’s analysis in
January 2018 used EDX, or energy-dispersive x-ray spectroscopy, a technique
that gives not only the elements present in a mineral, but their relative
proportions, which allowed Stan to calculate the chemical formula. The lead-iron
vanadate calderónite he found is intergrown with
descloizite, a lead-zinc vanadate. This probably indicates changing iron-zinc
concentrations in the fluids that precipitated the minerals. This represents just
the 11th documented calderónite
occurrence in the United States and the second in Montana. Stan identified the
first in Montana in the fall of 2017.
It’s an obscure mineral, and the crystals are tiny, but it
made this mineral collector’s day.
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