[meteorite-list] Cutting with water soluble oils?

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Thu, 9 Feb 2012 21:46:12 -0500 (EST)
Message-ID: <8CEB5B5493ABA04-104C-381B_at_webmail-d182.sysops.aol.com>

Erik asked:

"Is it okay to cut chondrites with water soluble oil in an oil saw or
will that screw with the classification?"

Hi Erik,

The question seems to ask if the classification of a chondrite can be
changed by getting it soaked in a water-soluble solvent.

No, I really doubt it would alter the classification, so in that sense
it would be fine. But ...

... the next question might be, is this a good idea, anyway and you
have some good answers to that already. Further, if we assume the oil
will be dipolar as well as hydrocarbon soluble at the same time, you
definitely don't want to use it on any *carbonaceous* chondrites as you
could leach out some interesting components of the meteorite and throw
it away with the waste-solvent.

If it is basically an *inorganic* (i.e., *not carbonaceous*) chondrite
there isn't much risk in my opinion in the near term if you use a clear
oil. The trouble could come into play in the near term if it is heat
dried, where some oils are subject to low temperature browning ... and
then over the long haul since the slice will last at least another one
billion years the oil can decompose all by itself and color the
meteorite which I think was the gistof another answer you had.

The use of water as a solvent has two competing ideas. First, since
the air is loaded with water, it is like you are adding nothing to the
meteoritethat wasn't already their except a quick liquid dip which most
chondrites have already experienced anyways. But that competes with
the idea that the liquid can transport contaminants such as oxidants
and rust catalyzers into the interior - and we've all see how some bad
cut jobs start showing leopard spots. So that covers the optimal trade
off of deionized water (or distilled water which is usually better if
 from the same vendor since it also removes uncharged atoms and
molecules disolved in the water as well).

But really soaking will alter the leachable mineral concentrations of
an inorganic meteorite too, though unless you are very specifically
looking for the pristine ratios, it makes virtually no difference for
chondrites that have been sitting in the desert.

That leaves the least invasive option of all. Dry cutting. But before
we pat ourselves on the back for having better methods than the King
lab, don't forget that a saw blade wears out more quickly dry causing
plenty of particles that will get all over the specimen anyway, since
the heat and no lubrication causes the welding of meteorite particles
to the sharp cutting piece tips on a microscopic level, leading to
their fracture and degradation of cutting properties - and many of the
hard cutting substances are carbon-based.

But what about a pure silicon based oil like a heat stable one maybe -
no clue. I don't know if they are used for cutting but it sounds lke
an expensive project, for our favorite silicates ... can't win ;-)

Kindest wishes
Doug
Received on Thu 09 Feb 2012 09:46:12 PM PST