[meteorite-list] 'Mars' meteorite

[Elton Jones]

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