Patterns in the compositions, properties, and geochemistry of carbonate minerals

A cyclic pH swing leads to the precipitation of magnesite plus minor amounts of aragonite after 37-42 days.

“The system is submitted to a cyclic pH swing, leading to the precipitation of magnesite plus minor amounts of aragonite after 37-42 days.7,20,[108][109][110][111]”

The tight cage arrangement in the R3̄C geometry of the magnesite structure reduces the degrees of freedom of the carbonate groups, which also hampers the precipitation step.

“Moreover, the tight cage arrangement in the R3 ˉC geometry of the magnesite structure reduces the degrees of freedom of the carbonate groups, which also hampers the precipitation step.17,20”

Disorder among the CO3 2- groups due to their limited degrees of freedom around the small Mg2+ cations may mean that the dolomite/magnesite problem is a stereochemical issue: strong electrostatic attraction to Mg2+ prevents rotation and tilting of the carbonate groups, hindering crystalline ordering in the precipitation step.

“The observations were associated to the disorder among the CO 3 2groups due to their limited degrees of freedom around the small Mg 2+ cations (radii of Mg 2+ is ca.30% smaller than Ca 2+ ), which may mean that the dolomite/magnesite problem is a stereochemical issue: the strong electrostatic attraction to the Mg 2+ cations prevents the rotation and tilting of the carbonate groups, hindering the”