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Dear Gasifiers/tarifiers:
Here is an additional note from John Humphrey on
Dolomite...
Tom Reed
Subject: Re: Pieces of Dolomite Puzzle
Tom,
You’ve captured the essence of
our conversation. Natural dolomites range from about 40 mol% MgCO3 up to
50 mol% MgCO3. “Young” dolomites tend to be less stoichiometrically
perfect (i.e., Ca-rich) and poorly ordered (i.e., not all cations moved to their
separate planes). The Ksp for well-ordered and stoichiometric dolomite is
about 10e-17, calcite is about 10e-8.5, and calcian dolomite varies with the
amount of excess Ca (but generally in the 10e-16.3 range and lower). I
really don’t know that much about the phase relations (high T stability, etc.),
but assume those relations should be consistent with the solubility differences.
I would check on the relative temperatures of dolomite versus calcite
decomposition if I were you. From there, you can assume that less perfect
dolomite should lie somewhere intermediate between ideal dolomite and
calcite.
Last Friday, at the Colorado School
of Mines Faculty club I met a geologist, John Humphrey, who knew more about
dolomite in 5 minutes than the dozens of users I have queried over 17 years
since then.
Thanks for the
plug and the flattery!
Cheers,
John
--
Dr. John D. Humphrey
jhumphre@mines.edu
Associate
Professor
john_d@humphrey.net
Dept.
of Geology and Geological Engineering
Colorado School of Mines
Golden, CO
80401 USA
(303) 273-3819; fax (303)
273-3859
http://www.mines.edu/~jhumphre
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