Hello Warin, Thanks for your explanation. It brought to mind a question I've had about certain meteorite thin sections I've seen for sale, one of which I recently purchased. In addition to the thin section, there is a scattering of thin flakes across the slide. Is this a reference material to determine the correct thickness of the section? These mineral flakes look nice all by themselves under x-polarized light. Thank you for your help. Best regards, Bob
Original Message: ----------------- From: Warin Roger [EMAIL PROTECTED] Date: Mon, 11 Sep 2006 06:46:45 +0000 (GMT) To: [EMAIL PROTECTED], [email protected] Subject: Re : [meteorite-list] Questions on olivine in meterorites. Hi Suzanne & Jim, all, A rock with olivine never contains quartz. In the presence of olivine, SiO2 produces pyroxenes. Quartz has a low birefringence, as opposed to olivine. Quartz polarizes in the light gray and white of the 1st order. In terrestrial rocks, it is thus easy to control the thickness of the thin section: quartz cannot be coloured in cross polarized light. It is thus necessary to thin the thin section to remove any colour in quartz. That's what's done for terrestrial rocks. In the frequent absence of quartz in meteorites, I think another reference is used, like the colour of feldspars. -------------------------------------------------------------------- mail2web - Check your email from the web at http://mail2web.com/ . ______________________________________________ Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
