[meteorite-list] 'Mars' meteorite

From: Elton Jones <jonee_at_meteoritecentral.com>
Date: Tue May 9 21:09:52 2006
Message-ID: <44613D55.4000903_at_epix.net>

Gary K. Foote wrote:

> It looks more like a huge hematite node. Even its crumbs are magnetic. Pieces from it are flakes, rather than 'chunks'.
>
>
Hello Gary,

I respect that you took the time to actually go see this over-hyped
paperweight . This is clearly a rock of igneous origin with minor
metamorphism possible. However the likely magnetic component is
magnetite for the following reasons.

While it is hard to do good ids from photos, Probability-wise this is
from a pegmatite which could be local or glacially transported in the
same vein(pun intended) as the deposits of Balmat New York or St
Lawrence County or even Quebec Canada. The mass looks like a classic
actinolite-tremolite-pyroxene group composition along with about 15-20
other minerals. The three which are likely the cause of the magnetic
attraction are Chromite(>2% chance) or Magnetite (>90%chance) and
secondary hematite (>5%chance). If there is a talc trend (aka
soapstone, greesy feel) or any iron sulfates ( brass-colored, metallic
flashes aka Pyrite Group) this indicates the mass had some hydrothermal
alteration and hematite could be present. In a non perfect world, I know
there is some hematite in the mass-the law of probability says so but on
the order of less than .001%. The law of probability also says the
magnetic attraction is due to magnetite in micro crystals within the
mass. Hematite is usually associated with sedimentary deposits but can
be found natively in metamorphic and igneous rocks.

Actually the composition of this mass has a lot in common with minerals
found in meteorites save for the hydrated silicates. The holes are
likely from areas that were more hydrated and thus softer than the
original pegmatite and therefore were gouged out during rough ice or
stream transport--(if not actually human made).

There is a long history of mining the magnetite deposits of New England,
while else where in on the east coast the desposit of iron are in the
from hematite and limonite(bog iron). Be it noted that hematite is no
always magnetically attracted.

 In addition to magnetite, which can be truly magnetic, there are
several other minerals that may be attracted to a magnet(anistrophy of
magnetic susceptibility(AMS)).
<http://www.galleries.com/minerals/property/magnetis.htm>

I am intrigued by the apparent attractiveness of the plant stems on your
magnet--any theories?

Elton
Received on Tue 09 May 2006 09:09:41 PM PDT