412 
MINERALS YEARBOOK, 1967 
 
ore, sand, slag, mill scale, air-entraining compounds, and grinding aids.
About 690 million kilowatt-hours of electrical energy was used. The wet process
was used at eight plants and the dry process at one. 
 The Medusa Portland Cement Co. plant at Charleviox started producing clinker
in August. The $25 million plant is located in a popular resort area on Lake
Michigan; to avoid air pollution and shoreline defacement, the company consulted
with local and State officials on all phases of the project during the planning
stages. The plant's 580-foot rotary kiln has been designed for production
of 4 million barrels of gray cement per year. An electrostatic precipitator
removes dust from kiln exhaust gases. The plant is highly automated; two
interconnected digital computers in a central control building will oversee
operations from the quarry to the finished cement silos. An automatic X-ray
spectrometer will analyze the quality of raw materials and the finished product.
The plant site is on navigable water, and 12 silos and five interstice bins
with a storage capacity of 250,000 barrels are located on an inshons slip.
The docking facility was designed to meet objections against structures extending
into Lake Michigan which might be unsightly or accumulate debris leading
to pollution. Lakeborne shipments will be made on the new 67,000-barrel capacity
cement carrier, the S.S. Medusa Challenger. Limestone is quarried on the
site from a deposit with an estimated 100-year supply. Shale and sand are
also available on the site. To help minimize blasting disturbance, a seismograph
has been installed 1½ miles from the quarry. 
 In November, Martin Marietta Corp. announced it has discontinued development
of a new cement plant at Milan, in southeastern Michigan. A severe water
leakage in the quarry at the new site was instrumental in the decision to
halt the project. Instead, it was announced, the company's plant at Essexville,
near Bay City, will be modernized and expanded. The plant capacity at Essexville
will be increased by 10 percent. One of the two kilns already delivered to
Milan will be moved to Essexville to replace four older, smaller kilns. The
second kiln and related equipment will be shipped to a new company plant
under development in Colorado. Grinding mills will be moved from Milan to
Essexville, a new raw mill will replace five mills, and a 
new finish mill will replace eight mills now in operation. 
 The Huron Cement Co. (Division of National Gypsum Co.) plant at Alpena marked
its 60th anniversary in January. With an annual rated capacity of 18 million
barrels, the plant is said to be the world's largest. Since the first cement
shipment in 1908, plant production has totaled nearly 258 million barrels.
Plant capacity is 30 times that of 1909, the first full year of production.
Future plans call for expansion of the plant to a 24-million-barrelper-year
capacity. 
 
 Clays.—Miscellaneous clays and shale were mined in 11 counties from
13 pits. Total output was slightly larger than in 1966. Increases in production
of material for manufacturing portland cement and lightweight aggregate offset
decreases in output for stoneware and heavy clay products. About 90 percent
of the production was used in cement manufacture. Of the remainder, 7 percent
was used for lightweight aggregate, and the balance for vitrifled tile, other
heavy clay products, and stoneware. The largest production was reported from
operations in Alpena, Antrim, Monroe, Saginaw, St. Clair, and Wayne Counties.

 
 Gem Stones.—Agates, thomsonite, and other semiprecious stones, as
well as specimens of native copper and hematite, were collected by hobbyists.
Most of the gem stones were found along Lake Superior beaches in the Upper
Peninsula. 
 
 Gypsum.—Smaller demand for building materials caused a decline in
crude gypsum output of more than 6 percent. Crude gypsum was produced in
Kent County from underground mines and processed at plants in Grand Rapids,
principally for plaster, lath, and wallboard. 
 In Tosco County, gypsum was quarried at Whittemore for portland cement retarder.
Quarries at Tawas City and Alabaster supplied crude gypsum for building material
plants at National! City, Detroit, and in Ohio and Wisconsin. Two deep water
ports were maintained at National City and Alabaster for lake transport of
gypsum materials. 
 
 Lime.—Increased demand for lime in basic oxygen converters and open-hearth
furnaces in steel plants, as well as in chem