From: James Rogers (jamesr@best.com)
Date: Tue Jan 29 2002 - 20:54:00 MST
On 1/28/02 3:45 PM, "Robert J. Bradbury" <bradbury@aeiveos.com> wrote:
>
> However, you may want to think twice before you go smelting
> the Fe2O3. I'm moderately certain hematite is a much better
> structural material than iron or steel excepting perhaps the
> property of ductility. It isn't as strong as Al2O3 (sapphire)
> but its still pretty good.
Yes, some mineral forms of iron oxide are extremely tough and durable,
although the really indestructible forms contain quantities of non-oxidized
metal. In fact, I have a minor anecdote about the toughness of certain
mineralized forms.
My parents lived on an island in Alaska that was about 150 square miles of
caldera remnants. However, on one lone peninsula off by itself, there was a
little yellow hill maybe 500 feet tall that was very different from the
surrounding geology. The yellow color of the hill was actually a layer of
surface oxidation on the black rock underneath, the monolith itself being an
unusual form of very metal rich basalt. One of the things that makes that
monolith special is that unlike the island it is found on, it is over two
billion years old, making it one of the older formations found in the world.
What was interesting about that rock hill was that it had rather extreme
mechanical properties and was nigh indestructible. The surface oxidation
layer acted as a protectant for the rock, allowing it to exist undegraded
after hundreds of millions of years in a very wet environment. Some
enterprising individuals tried to quarry the rock on a number of different
occasions for use as a building material with an extremely high compression
strength and fantastic wear and environmental resistance. The problem was
that the rock itself was too tough to cut. They could not find a cutting
edge that was both hard enough and tough enough to make quarrying the
monolith even vaguely economical. You had to use diamond edged tools to cut
the rock (which apparently was famous for shattering pickaxes and other
implements made with hardened tool steel), but even then the tools didn't
last long because the substrate holding the diamonds had a high failure
rate.
In any case, this rock was essentially a big chunk of iron rich basalt in an
unusual mineralized form, and it was apparently a substantially tougher
material than most of the things we think of as "tough". While it wasn't
quite as hard as Al2O3, it was almost certainly much tougher than Al2O3
(i.e. very resistant to shattering), which is arguably a fine trade-off as
it appears to be at least as hard as most metal carbides and nitrides.
Cheers,
-James Rogers
jamesr@best.com
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