Circular 47—High-purity dolomite deposits of southcentral New Mexico

By F. E. Kottlowski, 1957, 43 pp., 1 table, 4 figs.

Almost unlimited deposits of high-purity bedded dolomite, which could be utilized for the production of metallic magnesium and magnesium compounds, occur in south-central New Mexico, in the area from the Sacramento Mountains west to Deming, and from the northern tip of the San Andres Mountains south to Mexico. Iron-ore and silica sands, which could be used to make the ferrosilicon necessary to silicothermic production of magnesium metal, are present in large amounts in the same area. Large amounts of natural gas are available as a source of power, there is an adequate pool of inexpensive labor, and the warm climate would allow continuos operations.
The Ordovician Upham dolomite and the Silurian Fusselman dolomite are high-purity beds in most of the area. The Upham dolomite, 50–120 ft thick, contains an average of more than 21.3% magnesium oxide and less than 1.4% insoluble residues. The Fusselman dolomite thickens southward from a knife edge in the northern San Andres Mountains, to more than 850 ft in thickness in the southern Franklin and Florida Mountains, although some of 21.5% magnesium oxide and 0.7% small-size insoluble residues.

The Ordovician Cutter and Aleman Formations, which range from 50 to 500 ft in combined thickness, are mostly dolomite. The Cutter dolomite, however, includes argillaceous and limy beds that would need to be rejected selectively in the mining of high-purity dolomite. The Aleman dolomite contains 5–60% chert, which would have to be removed by flotation to produce high-purity dolomite. Some of the Permian carbonate beds in southern New Mexico are of high-purity dolomite, but are in relatively inaccessible localities. The object of this preliminary estimate of high-purity dolomite deposits in NM is to bring to the attention of producers and consumers of magnesium and magnesium compounds the large reserves of high-purity dolomite within the state. The dolomite deposits of NM are hundreds of miles closer to the consuming centers of the east than many western dolomite deposits utilized during WWII and during the Korean emergency, and they are near extensive gas and oil fields which can provide large quantities of inexpensive power. Although current freight rates are too high to make the transportation of NM dolomite to eastern processors feasible, the location of NM, almost 1,000 mi from any shoreline, is of obvious strategic advantage in wartime, and suggests that magnesium plants constructed near the dolomite deposits of NM would be far less vulnerable to attack than the magnesium plants of the east and west coasts.

The processing of dolomite in NM would require use of the silicothermic production method, which is relatively more expensive than the electrolytic method utilizing sea water and has been employed only during times of national emergency when support by Federal subsidy was possible. Canada, however, with almost unlimited resources of hydroelectric power, has two magnesium plants, and the larger of those is a silicothermic plant having an integrated ferrosilicon supply.