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In the context of crystal growth, particularly saddle or baroque dolomite development, what does "preferential lattice expansion due to excessive magnesium adsorption" mean in practical terms?

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Dolomite is a form of calcite in which magnesium replaces some percentage of the calcium in what is otherwise a calcium carbonate rock. Magnesium has the same charge, and thus bonding behaviours, as calcium but is physically a larger atom. At a low replacement percentage this size difference doesn't distort the calcite crystal lattice to a noticeable degree. In dolomites with a higher percentage of magnesium the crystal lattice distorts notably making the dolomite less physically stable than pure calcite, at really high, or "excessive", percentages of replacement the calcite lattice structure expands out into a predominantly magnesite lattice structure which is geometrically similar but with wider spacing at the atomic level.

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