[meteorite-list] 'Mars' meteorite

[Bill Southern]

A simple streak test will ID either..

Magnetite - greasy black or grey streak

Hematite - Reddish to rust brown streak

On unglazed porcelain.

Bill

--- Elton Jones <jonee at epix.net> wrote:


> 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

> 

> 

> 

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