[meteorite-list] Petrologic Groups

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:08 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C8692C5EFC_at_US-Torrance.mail.saic.com>

Hi Robert,

> Can or would anyone on the list take a moment and explain to me the
> 1-10 subgrouping system on the petrologic group 3's?

Can't help you there. All I know is that it is not
something that can be done visually.

> Also, could someone please explain how a chondrite achieves a petrologic
> classification with a range (ie H3-5 or L3-6)?

Breccia?

> And question number 3... Is it typically, or even consistently possible,
> with visual examination alone, to distinguish a Carbonaceous Chondrite
from
> an L or H class Chondrite?

Carbonaceous from L, H, or LL -- certainly in most cases.
The lower density of a carbonaceous chondrite would be a
big tipoff, even if they weren't so visually different.

> An LL from an L class? Or an Enstatite from a more common H (or L)
class?

It's been my experience that telling H from L is hardest.
LL should be easily distinguishable from H, and not that
much harder to tell from an L. I'll leave someone else
to answer about enstatite, since I've only seen pictures
and never looked at one under magnification.

Cheers,
Rob
Received on Fri 09 Feb 2001 02:56:52 PM PST