78 



UNITED STATES MINERAL RESOURCES 



sulfate (barite), which accounts for the low con- 

 centration of barium in sea water. 



Connate brines of many sedimentary formations 

 contain barium chloride (BaCL) which on mixing 

 with sulfate-rich waters will yield a precipitate of 

 barite. This process has caused problems in oil field 

 operations, notably in the Wilmington (Long Beach, 

 Calif.) oil field (Gates and Caraway, 1967). 



The geochemistry of barium is complex. More in- 

 formation and many references are available in the 

 works of Rankama and Sahama (1950), Graf 

 (1960), and Friedman (1969). 



ORE MINERALS OF BARIUM 



Barite, the chief ore mineral of barium, when 

 pure, has a specific gravity of 4.5, has a hardness 

 of 3 on Mohs' scale (in which the hardness of a 

 fingernail is about 1.5), and contains 58.8 percent 

 barium and 41.2 percent sulfate. The mineral occurs 

 in assorted colors, although shades of white to dark 

 gray and black are common in commercial deposits. 

 Barite crystallizes in the orthorhombic system and 

 commonly forms prismatic or tabular crystals. Gen- 

 erally it is found in irregular masses, concretions, 

 nodules, rosettelike aggregates, and in massive to 

 laminated beds. Mine-run ores contain some inclu- 

 sions and intergrowths of other minerals as well as 

 small amounts of other elements (Brobst, 1958, p. 

 80-81). Barite of vein and residual deposits com- 

 monly contains several percent strontium. 



Barite is most commonly associated with quartz, 

 chert, jasperoid; calcite, dolomite, siderite, rhodo- 

 chrosite, celestite; fluorite; and various sulfide min- 

 erals, such as pyrite, chalcopyrite, galena, sphalerite, 

 and their oxidation products. Ferruginous clays 

 make up a large part of residual deposits of barite. 

 Barite is a common gangue mineral in many types 

 of ore deposits, especially in veins that are mined 

 principally for other commodities, including lead, 

 zinc, gold, silver, fluorite, and rare-earth minerals. 

 Barite is a common constituent of some siderite-rich 

 iron deposits in Europe, but deposits of this type 

 have not been found in the United States. 



Witherite (BaCOa, barium carbonate, 69.6 per- 

 cent Ba and 30.4 percent CO3), a highly desirable 

 source for the production of barium chemicals be- 

 cause of its solubility in hydrochloric acid, occurs 

 as a minor accessory mineral in some barite depos- 

 its. Like barite, this mineral also crystallizes in the 

 dipyramidal class of the orthorhombic system. 

 Witherite has a hardness of 3-3.5 on Mohs' scale 

 and a calculated specific gravity of 4.29. In the 

 United States, only the El Portal mine, Mariposa 

 County, Calif., has produced witherite in large 



amounts ; operations ended there about 1950. Nearly 

 all the world's supply of witherite in 1972 came 

 from the Settlingstones mine, Northumberlandshire, 

 England. Witherite is probably only a very small 

 part of the barium resources of the world. 



Sanbornite (BaSi205), which contains 50 percent 

 barium, is of potential interest as a source of 

 barium for chemicals because, unlike many silicate 

 minerals, it is soluble in acid. The solubility permits 

 the recovery of the barium by further chemical proc- 

 essing. The mineral, formerly considered rare, has 

 been found in abundance associated with other 

 barium silicate minerals in contact with meta- 

 morphic rocks, mostly quartzite, in roof pendants 

 of the Sierra Nevada batholith in Fresno County, 

 Calif. (Matthews and Alfors, 1962). The resource 

 potential of sanbornite deposits is virtually un- 

 studied. 



Barium occurs in other minerals, but in concen- 

 trations so low that none of the minerals are likely 

 to be potential sources of the element. 



TYPE OF DEPOSITS 



Barite occurs in many geological environments 

 in sedimentary, igneous, and metamorphic rocks. 

 The geologic relations of three major types of com- 

 mercial deposits, the vein and cavity-filling, the 

 residual, and the bedded deposits, have been sum- 

 marized by Brobst (1958). 



Some recent references to the geology of barite 

 are given in this report; others are available in an 

 annotated bibliography by Dean and Brobst (1955), 

 and in a pamphlet included with a map (at a scale 

 of 50 miles to the inch) which shows the size and 

 distribution of deposits in the United States (Brobst, 

 1965). A summary of the geology and reserves of 

 barite deposits of the world (Brobst, 1970) also 

 includes a bibliography of about 100 references to 

 deposits outside the United States. 



VEIN AND CAVITY-FILLING DEPOSITS 



The vein and cavity-filling deposits are those in 

 which barite and associated minerals occur along 

 faults, gashes, joints, bedding planes, breccia zones, 

 and solution channels and in various sink structures. 

 The deposits in solution-channel and sink structures 

 are most common in limestone. The host rocks are 

 of Precambrian to Tertiary age in the United States. 

 Many deposits in the Western States are associated 

 with igneous rocks of Tertiary age, although nota- 

 ble exceptions are vein deposits of barite and rare- 

 earth minerals associated with igneous rocks of 

 Precambrian age at Mountain Pass, San Bernar- 

 dino County, Calif., and in the Wet Mountains, 



