Ocean Minerals 
Sub-Bottom 
Bottom 
(loosely consolidated) 
Deep Ocean 
(basaltic rock 
which may con- 
tain chromite, 
platinum, etc.) 
Continental Shelf 
Igneous and 
metamorphic 
rocks contain- 
ing vein and 
massive deposits 
of non-ferrous 
and precious 
metals 
Sedimentary 
(oil, gas, 
sulfur, 
coal, 
iron) 
Figure 45. Categories of ocean minerals. 
costs are high because the target (deposit) is 
concealed, but the industry has had long experi- 
ence on land in searching for concealed targets. 
Once an oil or gas target is discovered, the 
discovery hole can be converted into a producing 
well more readily than for hard minerals. More- 
over, because of highly developed geophysical and 
geological techniques used in locating oil and gas 
reservoirs, the ratio of target discovery holes to 
total exploration holes is high—on the order of one 
in five in the Gulf of Mexico (one in 13 country- 
wide, onshore and offshore). 
On the other hand, the hard mineral explorer is 
faced with an entirely different set of problems 
than the oil explorer. Most rich ore deposits that 
have sustained our Nation to the present time were 
exposed at the surface and discovered by surface 
prospecting. Only in the last 15 to 20 years has the 
mining industry seriously attempted to find de- 
posits not indicated by surface characteristics. 
Techniques to discover concealed subsurface 
mineral deposits on land are less developed than 
those for oil and gas. Offshore, virtually a whole 
new technology to discover sub-bottom lode and 
bedded deposits will have to be devised. Further, if 
Chemical 
precipitates 
(manganese, 
phosphorite 
nodules and 
Biological 
silos crusts) 
Oyster 
Detrital 
(sand, 
gravel, 
placers) 
Deep ocean 
sediments 
(red clay, 
oozes, etc.) 
a mineral discovery is made offshore the drill hole 
cannot be utilized as a producing unit. At that 
point, the explorer must decide whether to risk 
investing a large amount of capital to delineate the 
deposit to determine its potential profitability. 
The transition from discovery drill holes to an 
operating hard rock mine will require either 
development of a very large open pit or the 
penetration of the ore body by a vast underground 
network of tunnels and excavations. 
Oil and mineral targets differ in relative size. Oil 
targets may be tens of miles across, while some 
great metal deposits are tiny by comparison. For 
example, one of the largest copper deposits in the 
world is only about one square mile in horizontal 
area. This compares with an average of more than 
three square miles for the more than 200 oil 
reservoirs that have been developed in offshore 
Louisiana. Thus, the ability to discover deposits in 
certain formations and structures appears to be 
greater for oil than for hard minerals. 
Whereas a single test hole can indicate the oil 
and gas potential of a formation over a compara- 
tively large area, hard mineral exploration requires 
extensive close-spaced drilling to determine poten- 
VI-181 
