Mineral amount

[rapheul]

Hi, there,
I have a simple question about mineral amount calculation. For some reasons, I did not do the XRD test but instead, did the XRF test, but now I need the parameter for each single mineral amount that will be dissolved in the water when input equilibrium phases, I wonder how I should estimate the amount according to XRF test. For example, a limestone sample, which contains Ca 400k ppm, means 40% calcium content, is that saying the core has almost 100% calcite or(if we assume it mainly has calcite, Ca takes around 40% weight percent)? than if so, with the rock dry density of 2.7kg/L, there will be 27 mol calcite per liter! Is that too much mole calcite or still reasonable? Is the calculation correct?
Thanks a lot in advance!

[dlparkhurst]

Calcite solubility is on the order of 10 millimoles, so in most batch calculations, the presence of more calcite than that is sufficient to attain equilibrium. In transport calculations, the amount may make a difference, but again there is a point, say millimoles to a mole, beyond which there is still sufficient calcite to always attain equilibrium.

[rapheul]

Hi David, thanks for your quick reply!
So is that to say, the amount will actually not affect the simulation result when you are sure that you have more than that milimole calcite beyond its solubility? 
I am doing transport of this, then if I understood correctly, the amount value of calcite per liter which I input for limestone aqufier zone does not matter much to the transport process, is it right? But if you know the rock has also tiny percent of other mineral, which is maybe less than its solubility, or despite sufficient it may be consumed by some reactions, then in these cases, the amount of it may now be important, is this correct?

[dlparkhurst]

Yes. I think in general, the big changes would occur when you completely remove a mineral.