Re: Interplanetary dust particles: reproducing GEMS-like structure in the laboratory (Forwarded)

Andrew Yee wrote:

The varied
compositions of the GEMS make it difficult to arrive at a consensus
regarding their origin and formation process.

The glassy substance in GEMS is forsterite, Mg2SiO4. The SiO4
portion, as well as the entire salt, requires water for its formation.
Si* + 4 H2O ---> H4SiO4 (silicic acid) + 2 H2
Water is also the preferred medium for the formation of sulfides
in GEMS. Free metals in GEMS require a reducing environment,
such as hydrogen.
Aqueous and reducing conditions exist around evolved stars,
whose temperatures are below sun spot temperature (3500 ? K),
where water first appears. Subsequent reactions around evolved
stars are water-based, such as the formation of carbon monoxide:
C* + H2O ---> CO + H2
A closer picture of these aqueous reactions can be gained from
an inspection of the deep sea volcanos, where conditions are
also reducing; note the presence of silicic acid, sulfides,
hydrogen and forsterite in basalt:
http://www.pmel.noaa.gov/vents/chemistry/images/vents2.gif
John Curtis

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