Aragonite question

What is the difference between aragonite, calcite and dolomite?

I have found reference to the difference in buffering capabilities, but
what is the difference as far as actual composition?

Thanks,
Mark
.

Relevant Pages

  • Re: Mineral analysis may reveal life on Mars
    ... The researchers took 12 terrestrial calcite samples - from sources representing all three types of the mineral - to see if they could detect differences among them. ... Naturally, because of the structure of dolomite, it is going to have a looser structure than CaCO3... ... While it is generally true that the dolomitization process destroys biologic structures, there are a lot of dolomites that contain abundant fossils. ... Mississippi is the secondary dolomitization of many/most of the thick Missouri layers were related to the movement of 100 degree C+ highly mineralized fluids squeezed through the subsurface in association with the precipitation of the MVT lead/zinc deposits concurrent with the Ouachita uplift further south in AR and OK. ...
    (sci.geo.geology)
  • Re: Mineral analysis may reveal life on Mars
    ... > George wrote: ... > calcite, then, if it continues, ultimately to secondary dolomite. ... > calcite...and dolomitization often destroys any fossil evidence present ...
    (sci.geo.geology)
  • Re: Mineral analysis may reveal life on Mars
    ... The researchers took 12 terrestrial calcite samples - from sources representing all three types of the mineral - to see if they could detect differences among them. ... This weakening was detected when the researchers steadily heated the samples and noted when they began to lose mass by decomposing into gaseous carbon dioxide. ... not just a way to weaken calcite...and dolomitization often destroys any fossil evidence present in the original limestone. ... Naturally, because of the structure of dolomite, it is going to have a looser structure than CaCO3... ...
    (sci.geo.geology)