UNITED STATES MINERAL RESOURCES 



MAGNESIAN REFRACTORIES 



By Alfred J. Bodenlos and T. P. Thayer 



CONTENTS 



Page 



Abstract of conclusions 379 



Introduction 379 



Exploitation 380 



Geology 381 



Mineral deposits 381 



Magnesite 381 



Prospecting 382 



Genesis 382 



Brucite 382 



Olivine 382 



Other sources 382 



Resources 383 



Identified and hypothetical resources 383 



Speculative resources 383 



Problems for research 383 



Selected references 384 



FIGURE 



Diagram showing use of the principal raw ma- 

 terials of magnesium 



ABSTRACT OF CONCLUSIONS 



380 



Magnesium-bearing compounds are processed into high- 

 temperature refractories, indispensable as linings in modern 

 steel furnaces; chemicals; and magnesium, the lightest of 

 structural metals. They are derived from minerals, brines, 

 and sea water. 



Resources from which magnesium-bearing compounds may 

 be recovered range in sIm from large to practically unlimited 

 and are globally widespread. Identified resources of magne- 

 site throughout the world total 12 billion tons, and those 

 of brucite several million tons. Resources of dolomite, forster- 

 ite, and the magnesium-bearing evaporite minerals are 

 enormous; magnesium-bearing brines must constitute a re- 

 source of billions of tons; and the resource contained in sea 

 water is practically unlimited. The magnesium industry is 

 highly competitive, and more costly sources, such as evaporite 

 minerals, are little used. The bulk of magnesium-bearing 



compounds and the metal are recovered in the United States 

 from sea water, brines, and dolomite, and elsewhere in the 

 world from magnesite. 



Magnesite deposits still are being sought, particularly 

 those low in lime content. Opportunity for discovering such 

 deposits in the United States is judged to be small, but is 

 somewhat better in other parts of the world. 



INTRODUCTION 



Magnesium compounds are used to prepare re- 

 fractories and chemicals; high-temperature refrac- 

 tories are indispensable as linings in modem steel 

 furnaces and in certain parts of base-metal smelters, 

 and reactive magnesium chemicals have many well- 

 established industrial and pharmaceutical uses. 

 Magnesium is the lightest of the structural metals 

 and is used either as the pure metal or as an alloy' 

 wherever weight is a critical factor; magnesium 

 competes with aluminum for these purposes to the 

 extent that its higher price will allow. Magnesium 

 metal also is used as a reductant in the extraction 

 of titanium and certain other metals and as an 

 oxygen scavenger; it is an important military in- 

 cendiary material (Comstock, 1963; and Paone, 

 1970). 



Magnesium-bearing raw materials are abundant, 

 geographically widespread, and strongly competitive 

 in world markets; they consist of minerals and 

 brines of various geological origins (Davis, 1957 ; 

 Birch and Wicken, 1951; and Wicken, 1960). This 

 chapter, however, deals principally with the re- 

 sources of magnesite, brucite, and olivine. Resources 

 of dolomite, evaporites, and brines are described in 

 other chapters of this volume. 



Uses of the principal raw materials are shown 

 in figure 44. 



Magnesite and brucite, when calcined at low tem- 

 perature (1,600°F) yield reactive or caustic-calcined 

 magnesia that is used to make chemicals and ce- 

 ments. Magnesite and dolomite when calcined at 

 high temperatures (3,000°F-4,000°F) yield inert 



U.S. GEOL. SURVEY PROF. PAPER 820 



379 



