Sonny, Martin, Charlie and others,
Thanks to all who continue to report in on the condition of their PV
specimens. Of all those that have responded, only one person has stated that
his piece has a couple of small spots of oxidation, and as he added: " I had to
look good, you understand, the slice still looks great." But, I am going to
contact that collector privately and ask him " IF " it might NOT be rust
after all, and perhaps could be explained by the following from Sonny:
" The cut surface appeared to have rust stains along the interior in
numerous locations. Upon closer inspection they were actually crystal
structures / apatite."
I definitely know what Sonny is talking about here. I vividly remember the
first time I saw either apatite (or perhaps more likely, MERRILLITE---see
below) crystals in the cut face of a PV slice. I immediately thought it was a
small area of rust, but just as Sonny reports, I discovered its true nature
upon closer examination.
Below is part of an article in the May 1999 issue of Meteorite magazine on
phosphates in the Portales Valley meteorite that might explain how very tiny
"spots of what appear to be rust" might actually be the yellow grains of
merrillite?????
" Maybe one of the most spectacular meteorites to have fallen to earth is the
anomalous Portales Valley chondrite that touched ground in New Mexico in June
1998. It show chondritic clasts of ( H type ) that are embedded in metal veins.
In slabbed samples, this attractive and unusual texture is very striking. On
cut surfaces, one may also notice some gray and YELLOW, glassy grains situated
between metal and chondrite...... The gray grains yield a spectrum typical of
apatite, a calcium phosphate that was known from meteorites before but is rare
in this size. The YELLOW mineral turns out to be be merrillite, a very rare
mineral only known in small quantities and sizes from a few meteorites ( such
as Allegan, Bjurbole, Homestead, Shergotty, Waconda, and a few others).... It
turns out that Portales Valley may have just gotten even more interesting: A
chondrite containing the largest know merrillite crystal grains known!"
Meteorite, May 1999
I may be way off base on this, but it is my belief that what I first thought
to be very tiny spots on PV slices are in fact the yellow grains of merrillite(
or perhaps apatite, as Sonny states).
Once again, I would appreciate any thoughts from others on this.
Sincerely,
Robert Woolard
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