THE MINERAL INDUSTRY OF MINNESOTA 437 
 
 Studies were continued by the University of Minnesota Mines Experiment Station
regarding recovery of manganese from Cuyuna Range manganiferous ores by various
leaching processes. 
 At its Twin Cities Metallurgy Research Center, the Federal Bureau of Mines
conducted research on the extraction of both iron and manganese products
from lowgrade Cuyuna Range ores by roasting and autoclave techniques. 
 
 Iron and Steel.—American Steel & Wire Division of United States
Steel Corp. produced basic pig iron, steel, and coke at Duluth. In mid-1967,
North Star Steel Co. began operating a 50-ton capacity electric furnace at
St. Paul, producing steel from ferrous scrap. 
 
NONMETAIS 
 
 Abrasive Stone—The Jasper Stone Co. produced grinding pebbles and
tube-mill liners from a quartzite deposit near Jasper, Rock County. Sales
of both types of material decreased in quantity but increased in value from
those of 1966. 
 
 Cement.—Portland and masonry cements were manufactured at Duluth by
Universal Atlas Cement Division of United States Steel Corp., the State's
sole producer. Shipments of portland cement remained virtually unchanged
in quantity but decreased in value from those of 1966 because of a decline
in sales of higher valued portland slag-cement and an increase in sales of
types I and II (general use and moderate heat) cement. Masonry cement shipments
declined from those of 1966 while shipments of portland cement to ready-mixed
concrete companies, highway contractors, and other contractors increased.
Sales to building material dealers, concrete manufacturers, and government
agencies declined. Raw materials used in the manufacturing process included
limestone from Michigan, slag from the nearby U.S. Steel blast furnaces,
sand, bauxite, gypsum, iron dust, and air-entraining compounds. Three rotary
kilns were operated, using bituminous coal and natural gas for fuel. Shipments
were primarily to Minnesota consumers, with lesser amounts shipped to Iowa,
Michigan, North Dakota, South Dakota, and Wisconsin. Most of the cement was
transported in bulk by rail and by truck. 
 Shipments of cement to and within Minnesota in 1967 were about 8.4 million
barrels of portland cement and 419,000 barrels of masonry cement, representing
an increase of 2 .percent and a decrease of 3 percent, respectively, from
those of 1966. Shipments were received from plants in 11 other States during
1967. 
 Dundee Cement Co. finished construction of its distribution center on the
Upper Harbor of the Mississippi River at Minneapolis. Huron Cement Co., Division
of National Gypsum Co., began construction of a distribution center, also
located in Minneapolis. 
 
 Clays.—Miscellaneous clay and shale was produced in Brown, Carlton,
Hennepin, Ramsey, and Redwood Counties. Production increased about 2 percent
in quantity and value. Chief reason for the increase was a greater demand
for material used in production of lightweight aggregate. Material was also
used for the manufacture of building brick, and floor and wall tile. Output
of fire clay, all of which was used in the manufacture of vitrified sewer
pipe, increased in quantity and value from that of 1966. 
 The Minnesota Geological Survey continued its investigation of kaolin and
other clay resources of the State. The purpose of this study was to provide
geologic data useful in developing Minnesota's clay resources. Included in
the study were clays and shales from the Minnesota River Valley in Brown,
Redwood, Renville, and Yellow Medicine Counties; along the Mississippi River
between Little Falls and St. Cloud; an area near Austin, Mower County; and
the Glenwood and Decorah Formations in southeastern and east-central Minnesota.

 At its Twin Cities Research Center, the Federal Bureau of Mines continued
testing the suitability of clays from a portion of the glacial Lake Agassiz
basin in St. Louis County for use as taconite concentrate binder. A paper
concerning this research was presented at the Minnesota Section A.I.M.E.
meeting in Duluth. 
 
 Gem Stones.—Minor quantities of semiprecious gem stones, principally
agates, were collected by hobbyists. Gem materials were found chiefly along
the north shore of Lake Superior, along the Mississippi River, and in gravel
pits in the south-