442 MINERALS YEARBOOK, 1967 
 
 Quartzite was produced in Nicollet County near New Ulm and in Rock County
near Jasper. Output was used for concrete aggregate and roadstone, filters,
furnace and converter linings, railroad ballast, riprap, rubble, and other
purposes. 
 Crushed and broken basalt was produced near Duluth, St. Louis County, mainly
for concrete aggregate and roadstone, with a lesser amount used for riprap.
Production decreased substantially from that of 1966. 
 Marl, for agricultural purposes, was produced in Cass and Wadena Counties.
Output decreased from that of 1966. 
 
 Sulfur.—The Great Northern Oil Co. and Northwestern Refinery Co. recovered
elemental sulfur, as a byproduct, at refineries near Pine Bend, Dakota County,
and St. Paul Park, Washington County. The latter company began recovering
sulfur in July, utilizing the Modified-Claus process. Shipments increased
both in quantity and value from that of 1966. 
 
 Vermiculite.—Exfoliated vermiculite was produced from crude material
mined outside the State at two plants in Minneapolis, Hennepin County, and
one in St. Paul, Ramsey County. Total value of output re 
mained about the same as in 1966, but the quantity decreased about 2 percent.
The exfoliated material was used for various types of insulation, plaster
aggregate, concrete aggregate, and agricultural purposes. 
 
MINERAL FUELS 
 
 Pcat.—Increased demand for peat was evidenced by the 1967 shipments
of nearly 14,000 tons which almost equaled the record output of 1964. Production
of both moss and reed-sedge peat increased significantly in quantity and
value over that of 1966. No shipments of humus peat were recorded in 1967.
Peat was produced by five companies in Aitkin, Becker, Carlton, Itasca, Otter
Tail, and St. Louis Counties. Material was sold in bulk and in packaged form
and was used for general soil improvement, packaging shrubs and other plants,
and as an ingredient for potting soils. A 3-year research project was planned
by the Minnesota Iron Range Resources & Rehabilitation Commission to
examine the possibility of using peat as a waste stabilizer in polluted water.
The project would be financed by a grant from the Federal Water Pollution
Control Administration, Department of the Interior.