PROSPECTOR finds molybdenum

In Science of 3 September 1982 Campbell, Hollister, Duda and Hart reported that the expert system PROSPECTOR, given geological maps drawn before drilling and rules from a porphyry molybdenum specialist, identified on Mount Tolman in Washington State the location of previously unknown ore-grade mineralization.

The system was built in the Artificial Intelligence Laboratory of SRI International; at the time of the paper Duda and Hart were at the Fairchild Laboratory for Artificial Intelligence Research in Palo Alto, and the rules came from a porphyry molybdenum specialist. The Christian Science Monitor of 30 September 1982 quoted Rene Reboh, project director of SRI's Expert Systems Program: each expert was questioned for about fifty hours, and program and expert agreed on the same problems to within 6 or 7 percent on average; those are the developer's words. How PROSPECTOR reasoned is set out in an SRI technical note of June 1981. Every statement in a model has a prior probability; a rule multiplies the odds of a hypothesis by a sufficiency measure when the evidence is observed and by a necessity measure when it is absent, both given by the specialist. The geologist answers on a certainty scale from -5 to +5, where 0 means nothing is known; 'and' takes the smallest of the probabilities, 'or' the largest. To choose drilling sites the system took digitized maps, divided them into a grid of 128 by 128 points and ran the network 16,384 times to produce a colour-coded favourability map. What the record does not claim. The full text of the paper was not read (the publisher's page sits behind a Cloudflare check), and the 1981 note does not mention Mount Tolman, so the record does not describe how the finding was confirmed or how much ore was found.