THE MINERAL INDUSTRY OF MICHIGAN 
413 
 
ical manufacture, caused a 5-percent increase in State lime production. In
addition to these major consumers, smaller quantities of lime were used in
sugar refining, paper manufacture, water purification, and sewage treatment.
Lime plants were operated in eight counties, but four-fifths of the State
output was concentrated in Wayne County to meet requirements of steel mills
and chemical plants in the Detroit area. About 55 percent of the production
was used by the producers, and the remainder sold. Only 8 percent of the
total production was shipped to consumers outside the State. About 262,000
tons of lime (more than three-quarters of it quicklime) were shipped into
Michigan. Shipments originatIng in ' Ohio comprised most of the imports.
Data for lime regenerated at papermills, water purification plants, and acetylene
processors are exchsded from total State production. 
 
 Natural Salines.—Bromine, calcium chloride, calcium-magnesium chloride,
iodine, magnesium compounds, and potash were extracted from natural well
brines at chemical plants in Gratiot, Lapeer, Manistee, Mason, Midland, and
Wayne Counties. The total value of chemicals produced from natural salines,
excluding salt which is discussed below, was about the same as in 1966. In
June, Great Lakes Chemical Corp. closed its Filer City plant at which the
company produced elemental bromine. 
 
 Perlite.—Crude perlite, mined in Western States, was expanded at plants
in losco, Kent, and Wayne Counties. The material was used principally for
building-plaster aggregate. 
 Salt.—Salt was produced from an underground mine in Detroit, and recovered
from natural and artificial brines at plants in Gratiot, Manistee, Midland,
Muskegon, St. Clair, and Wayne Counties. Increased demand for salt by major
consumers in chemical manufacture, for road use, animal feed, and water softening
resulted in a 7-percent increase in production. Michigan salt was distributed
to 44 States and Canada. The largest out-ofState shipments were to Illinois,
Indiana, Minnesota, Ohio, and Wisconsin. 
 
 Sand and GraveL—Michigan continued to be a leading source of sand
and gravel production, the second highest in the Nation (after California).
Although tonnage was down about 5 percent, the increase in unit value from
$0.90 to $0.95 per ton raised total value to a record high of $49.6 million.
Demand fQr sand and gravel for building use increased about 3 percent; other
major uses registered declines—for paving material and fill (7 percent),
industrial sand (nearly 10 percent). Sand and gravel production was reported
from all counties except Bay, Benzie, Monroe, and Montmorency. The Detroit
area (Livingston, Macomb, Oakland, Washtenaw, and Wayne Counties) produced
19.5 million tons, or 37 percent of the State total. Production of more than
1 million tons was also reported from each of the following counties: Berrien,
Ingham, Kalamazoo, Kent, Ogemaw, Ottawa, and Tuscola. Over 93 percent of
the sand and gravel was processed. About 90 percent was moved by truck and
the remainder by rail and water. Production was reported from 374 commercial
and 108 Government-andcontractor operations.