[meteorite-list] PV, and Apatite or Merrillite

From: Robert Woolard <meteoritefinder_at_meteoritecentral.com>
Date: Tue, 16 Feb 2010 11:25:51 -0800 (PST)
Message-ID: <918460.20530.qm_at_web39607.mail.mud.yahoo.com>

 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















      
Received on Tue 16 Feb 2010 02:25:51 PM PST