[meteorite-list] Range of S.G.Values

From: David Gunning <davidgunning_at_meteoritecentral.com>
Date: Sun, 22 May 2011 09:55:11 -0400 (EDT)
Message-ID: <49793.74.209.45.243.1306072511.squirrel_at_webmail.fairpoint.net>

Hi All,

It's been pointed-out to me in a private email that two of the specific
gravity values cited in my recent post may be "suspect".

It's been suggested that the Tatahouine specimen "cannot be correct".
The reasoning is that "Tata is essentially a pyroxenite with the typical
composition of a diogenitic pyroxene of Fe 24, the SG would be at least
3.4."

After re-checking I can see that the correct specific gravity value for
this specimen is 3.34 and not the 1.43 previously arrived at. Ooops!

Thanks to Ted for pointing that out to me.

The other "suspect" reading is the "Allende" at 3.47. In rechecking I
arrive at the same specific gravity of 3.47 for the "Allende".

According to a 2002 paper by Britt and Consolmagno the specific gravity,
referred to as the "Grain Density", of the Diogenites ranges between from
3.30 to 3.47. A specific gravity of 3.34 is within that range of values.

The same 2002 paper cites the specific gravity of the Carbonaceous
Chondrites, including Allende, as having a range of specific gravity
values of between from 3.26 to 3.58. At 3.47 the specific gravity of the
Allende is within that range of values.

There are very few, if any, minerals on earth or from outer space that
have a firm and fixed specific gravity value. One that comes to mind is
diamond at 3.51, although it, too, can have a slight range of values.

The measuring of specific gravity, or "grain density", is a relatively
simple and inexpensive way to double check the likelihood that there has
been no mix-up in a given meteorite stated sample's pedigree.

Respectfully submitted,

David Gunning
Received on Sun 22 May 2011 09:55:11 AM PDT