--- MARK BOSTICK <[EMAIL PROTECTED]> wrote: I was wondering on the chromium aspect. I > know some of you are better geology people then me, > but wouldn't that be an emerald?
Chromium is one of the trace elements responsible for the "green" color in both diopside and emerald. Basic Diopside is ((Ca,Mg)Si2O6), Calcium Magnesium Silicate:an Inosilicate--(Single Chain)--a Pyroxene if you will, which is a class of minerals well represented in meteorites. Chrome diopside ((Ca,Na,Mg,Fe,Cr)2(Si,Al)2O6) is heavy in Cr and Fe. The existence of diopside in a meteorite is significant from a mineralogical standpoint owing that the ratios it forms with other pyroxenes above 900°C and below 700°C limit the situations where it can occur as large crystals. Emerald is the gem name for green beryl: Be3Al2(SiO3)6, Beryllium Aluminum Silicate, which is an which is a Cyclosilicate-Ring Silicate. Beryl, in any form, has not been found in meteorites(AFAIK). Beryl is rare anyway owing that the beryllium and chromium are usually scavenged away in formation. Thus it can only form emerald under very specific and rare conditions. Were it not for the beryllium these molecules would be pyroxene chains instead of rings. A cyclo-silicate is a chain silicate that links back on itself to form rings. As such, the two minerals are distantly related but form in very different environments. Scientifically interesting but probably mundane for the lay collector, by working backwards from the minerals found in meteorites we can understand the conditions in which they formed(composition, temperature, and pressure). Elton ______________________________________________ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
