Year and industry 
Average 
men 
working 
daily 
Days 
active 
Man- 
days 
worked 
(thou- 
sands) 
Man- 
hours 
worked 
(thou- 
sands) 
Number of 
injuries 
———~—-—-- — Fatal Non- 
fatal 
Injury rates per million man-hours 
Fre- Sever- 
quency ity 
1966: 
 
 
 
 
 
 
Nonmetal          
11 
296 
8 
26 
 
 
Sand and gravel     
69 
191 
18 
105 
 
 
Stone            Total            
1967:P 
10 
218 
2 
20 
 
 
 
90 
207 
19 
151 
 
 
 
 
 
 
 
 
 
Nonmetal          
15 
250 
8 
26 
 1 
38.46 154 
Sand and gravel     
75 
220 
17 
184 
 1 
7.45 171 
Stone            Total            
10 
218 
2 
20 
 
 
 
100 
223 
22 
180 
 2 
11.12 150 
P Preliminary. 
REVIEW BY MINERAL COMMODITIES 
 MINERALS YEARBOOK, 1967 sylvania and Maryland.222 
 
Table 3.—Employment and injury experience in the mineral industries

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
NONMETALS 
 
 Clays.—Miscellaneous clay was produced by Delaware Brick Co. from
an open pit mine near New Castle, New Castle County. All production was used
by the company in the manufacture of common red building brick. Under a cooperative
agreement between the Delaware State Geologist and the Federal Bureau of
Mines, samples from about 30 clay deposits in the State were taken and given
preliminary tests to deteruiine suitability for various ceramic and other
uses. Results of the tests are on open file at the State Geologist's office,
University of Delaware, Newark, Del. 
 Sand and Gravel.—Sand and gravel was produced in all three counties
of the State; the largest production came from New Castle County. Sand and
gravel continued to be the principal mineral of value produced in the State.
Production was reported by 16 companies, seven with preparation plants and
nine that ship bank-run material. 
 Of the total sand and gravel production, sand accounted for 29 percent of
tonnage and 33 percent of value. A total of 568,000 tons of sand was sold
in 1967, compared with 558,000 tons in 1966. Sand was used chiefly for building
and paving; about 312,000 tons was sold for building purposes and 225,000
tons for highway use; the remainder was used principally for fill 
and as engine traction sand. The average value, f.o.b. plant, remained at
$1.07 per ton. Values ranged from $0.80 to $1.47 for building and paving
sand to $0.35 for fill. Most of the sand for building and paving use was
processed. The tonnage sold as "pit-run" was chiefly for fill and engine
traction. Virtually all of the sand was delivered by truck. 
 Gravel production amounted to 1,398,000 tons, a 33-percent increase over
the 
1966 production of 1,052,000 tons. Chief use was in highway construction;
smaller quantities were used for building, fill, and other purposes. The
average value of gravel, fob. plant, was $0.89 per ton, compared with $0.81
per ton in 1966. Washed gravel ranged in price from $0.75 to $4 per ton,
and pit-run (unprocessed) gravel ranged from $0.35 to $0.75 per ton. Most
of the gravel was shipped by truck. 
 Stone.—Output and value of stone (gabbro) was about the same as in
1966. Gabbro was quarried near Wilmington, New Castle County; the stone was
classified as granite for statistical purposes. Most of the production was
crushed and sized as a concrete aggregate or as stone sand; a small quantity
was sold for riprap. 
 In addition to the stone produced in the State, a sizable tonnage of crushed
stone, used chiefly for highway construction, was purchased from sources
in Penn-