[meteorite-list] Classification for Novato (name pending approval)

From: Galactic Stone & Ironworks <*meteoritemike_at_meteoritecentral.com*> Date: Tue, 30 Oct 2012 10:52:07 -0400 Message-ID: <CAKBPJW_Pvk6DLDEVN=GonsMjhFa3qX+UQGj2+Rh259c--U_vog_at_mail.gmail.com> · meteoritemike_at_meteoritecentral.com

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On 10/30/12, Robert Verish <bolidechaser at yahoo.com> wrote:
> Greetings All,
>
> It is my distinct pleasure to have the honor of passing along the following
> characterization of the "Novato" meteorite.  Here is the message that I
> received from Dr. Alan Rubin:
>
> I just finished analyzing the Novato "N01" stone:
>
> It is an L6 breccia.  W0  S4
> olivine Fa 24.1?0.4 (n=21)
> Low-Ca pyx Fs20.7?0.5  Wo1.5?0.2 (n=22)
> Ca-pyx Fs8.0?0.7 Wo44.7?0.8 (n=5)
> The chromite grains are somewhat richer in Al2O3 (6.4 wt.%) and MgO (3.4
> wt.%) than unshocked OC chromite, but are more characteristic of shocked and
> shock-melted chromite grains.
> Most of the metallic Fe-Ni is taenite with 77.7?5.0 wt.% Fe, 21.4?5.4 wt.%
> Ni and 0.51?0.18 wt.% Co (n=18).  Only one kamacite grain was identified
> (7.2 wt.% Ni and 1.1 wt.% Co).
> The Co content of this single grain is intermediate between the ranges for L
> (0.70-0.95 wt.% Co) and LL (1.42-37.0 wt.% Co) chondrites, but is closer to
> L.
>
> Plagioclase: Ab86.0?0.6 Or7.0?0.4 (n=14) is richer in alkalis than typical
> OC plagioclase, and probably reflects shock melting.
>
> Troilite is essentially pure FeS; it contains no detectable Cr, Co or Ni.
>
> And as I said before:
>
> Silicates have weak mosaic extinction.  Plagioclase grains range from 50-200
> ?m.  There are lots of troilite veins going through large portions of the
> rock (silicate darkening).  Chromite grains are fractured; many have
> troilite veins transecting them.  There are a few chromite-plagioclase
> assemblages.
> I found one 12x20-?m-size grain of metallic Cu.
> Some of the troilite grains are polycrystalline.
> There are some patches where plagioclase has been melted and mobilized.
> There is localized melting around some of the metal and sulfide grains.
> There are a few silicate shock melt veins replete with small metal and
> sulfide blebs.  There are some chondritic clasts with far fewer veins that
> have moderately large, highly recrystallized barred olivine and porphyritic
> olivine-pyroxene chondrules that are well integrated into the matrix.  These
> chondritic clasts are much lighter-colored in transmitted light than the
> matrix of the rock.
>
> Please pass this info along to all interested parties.
>
> End of message from Dr. Rubin.
>
> With best regards,
> Bob V.
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