LOW–TEMPERATURE FORMATION
OF DOLOMITE AND MAGNESITE


J.C. DEELMAN

version 2.3 (2011)

     The way in which dolomite and magnesite form under conditions of low–temperature and atmospheric pressure has become known from reproducible laboratory experiments published in 1999.*  Earlier the author has shown how the hydration of magnesium ions cannot be held responsible for the reluctance of dolomite formation in low-temperature experiments.**  When precipitating mixed Mg ⁄ Ca carbonates first metastable precursors will form. Only through the introduction of intervals of dissolution alternating with the intervals of precipitation, more and more of the stable phases (dolomite and ⁄ or magnesite) will form. Read the complete text of my book, if you want to learn more about what once was described as "the dolomite problem".


TITLE PAGE, COPYRIGHT, DEDICATION, CONVERSION TABLE, CONTENTS & ACKNOWLEDGEMENTS

INTRODUCTION pp. 1 – 2

1. "DOLOMITIZATION" RECONSIDERED pp. 3 – 23

What diagenesis? – Models of "dolomitization" – High–temperature syntheses – Replacement – Laboratory evidence – Huntite and norsethite – Solid state diffusion – Microtextures – Discussion.

In this first chapter the process known as "dolomitization" is being reconsidered. It is shown, that it is a historical misunderstanding to believe, that at room temperature and under atmospheric pressure calcium carbonate will ever react with magnesium in solution to give dolomite.

2. SOLID SOLUTION OR SUPERLATTICE ? pp. 24 – 54

Mixed crystals – Structural chemistry – X– Ray analysis – Diffraction signal – Stacking faults– Stoichiometry – Magnesium calcites – Calcite, aragonite and dolomite – Discussion.

The phase relations in the system of the anhydrous carbonate CaCO3 and MgCO3 are discussed in chapter 2. It is concluded on the basis of a variety of physicochemical considerations, that the magnesium cation is far too different from the calcium cation to allow for any solid solutions. Mixed crystals between CaCO3 and MgCO3 consist of stacking sequences (as in the Mg calcites) or of superlattices (as in dolomite and huntite).

3. NEODOLOMITE RE–EXAMINED pp. 55 – 74

The precursor – Superstructure reflections – Degree of order – Formation of superlattices – Exsolution – Phase relations – Disordered dolomite? – Discussion.

At times the suggestion is being made, that a phase described as " protodolomite" (originally: "neodolomite") must be the precursor to dolomite sensu stricto. However the structural chemistry of "protodolomite" is identical with that of a magnesium calcite. Moreover the suggested conversion of "protodolomite" into true dolomite has never been observed to take place under conditions of room temperature & atmospheric pressure.

4. REGIONAL ASPECTS pp. 75 – 160

Introduction – Afghanistan – Australia – Austria – Bahamas – Belize – Bonaire – Botswana – Brazil – Canada – Chad – Colombia – Denmark – France – Germany – Ghana – Greece – Hungary – India – Indonesia – Israel – Italy – Jamaica – Japan – Libya – Mexico – Netherlands – Pacific atolls – Persian Gulf – Russia – Spain – Tanzania – Tunisia – Turkey – United Kingdom – United States – Dolomite in deep–sea sediments – Dolomite in caves – Discussion.

As will be demonstrated in Chapter 4 on the regional aspects of dolomite formation, there is a bewildering mass of indications as to the possible significance of fluctuations in the low–temperature formation of dolomite. Additional evidence was found in "static controls": in those environments lacking any marked fluctuations no dolomite was found. Mere deduction leads to the conclusion, that all it takes to form dolomite in the sedimentary environment is some form of fluctuation. With this observation in mind almost all of the known local parageneses of modern dolomite are being reviewed.

5. ORGANIC OR INORGANIC ? pp. 161–187

Introduction – Dolomite in reefs – Dolomite in peat and coal – Dolomite in dogs – Dolomite in pearls – Dolomite and algae – Dolomite and bacteria – Discussion.

In Chapter 5 the question concerning an organic or inorganic origin of dolomite will be considered. For numerous indications are known, pointing in the direction of active participation of for example algae or of bacteria in the low–temperature formation of dolomite.

6. MAGNESITE AND HUNTITE pp. 188 – 212

A. Magnesite: Introduction – Syntheses of magnesite – Occurrences of Recent magnesite – Amorphous magnesium carbonate – Hydrated magnesium carbonates – Dehydration barrier – Magnesia alba and hydromagnesite
B. Huntite: Introduction – Recent deposits of huntite.

In Chapter 6 almost all occurrences of modern magnesite are being reviewed, and speculations are offered concerning the possible dehydration of magnesium cations. In addition most of the information on the formation of huntite in the sedimentary environment is discussed.

7. DOLOMITE SYNTHESES pp. 213 – 275

General remarks – Irreproducible results – Scheerer´s experiment – Experiment by Pfaff – Experiments by Linck – Leitmeier´s experiments – Experiments of Lalou – Experiments of Zeller, Saunders & Siegel – Erenburg´s experiments – Budzinski´s experiment – Experiments by Oppenheimer & Master – Liebermann´s experiments – Experiments by Glover & Sippel – Experiment by Donahue & Donahue – McCunn´s experiments – Experiments by Mirsal & Zankl – Deelman´s experiments.

In Chapter 7 all of the known dolomite syntheses, that is to say all of the known claims on the low–temperature synthesis of dolomite, are not only being discussed, but also the duplications carried out are being described.

8. MECHANISM OF DOLOMITE FORMATION pp. 276 – 327

Nucleation and statistics – Stability and metastability – Breaking Ostwald´s Rule – Reversible or irreversible ? – Formation of magnesite – Dolomite formation – Replacement ? – Looking back (and forward).

The last chapter centres on the principle of "Breaking Ostwald ´s Rule", i.e., the way in which fluctuations are capable of changing the precipitation of mainly the metastable phase into precipitation of mainly the stable phase.

9. NOTES pp. 328– 364

In the main text of each chapter notes are indicated by superscript numerals.

REFERENCES

A – D pp. 365 – 390
E – K pp. 391 – 424
L – R pp. 425 – 458
S – Z pp. 459 – 483


A TRIBUTE TO OTTO LIEBERMANN pp. 484 – 485

TABLE II pp. 486 – 493

THE LIFE AND TIMES OF DÉODAT DE DOLOMIEU pp. 494 – 515



 *) LOW-TEMPERATURE NUCLEATION OF MAGNESITE AND DOLOMITE, Neues Jahrbuch für Mineralogie, Monatshefte, Jg.1999, pp.289–302.

**) LOW-TEMPERATURE SYNTHESIS OF EITELITE, Na2CO3·MgCO3, Neues Jahrbuch für Mineralogie, Monatshefte, Jg.1984, pp.468–480.

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Contact the author at:   J.C.Deelman@demon.nl