While the prosecution in the Abscam bribery trial of Sen. Harrison A. Williams Jr. (D-N.J.) used secretly recorded videotapes of the senator with a frictitious Arab sheik to state its case, the defense continued today to turn the coutroom into a sort of geology class.

For the second day in a row, Williams' attorney, George K. Koelzer, called witnesses to testify that the Virginia titanium mine central to the charges was a legitimate venture designed to produce paint pigment, not strategic metal needed by the government.

Thus the jury heard a detailed description of the technical merits of ilmenite, nelsonite and apatite -- mineral ores found in the mines on the Piney River in Nelson County.

Williams and codefendant Alexander Feinberg are charged with bribery and conspiracy for promising to use the senator's influence to get government contracts for titanium in return for a $100 million loan from the "sheik" to develop the mine. Williams allegedly held a hidden interest in the mine, which he thought would be worth $12.6 million.

Koelzer said in his opening statement to the jury that the senator was fooled by the undercover FBI agents into bragging about his influence. But he said the senator and his alleged co-conspirators never intended to produce titanium metal -- a highly prized lightweight metal used in fighter planes and submarines -- until government agents insisted on it.

Through he has never mentioned the word entrapment to the jury, Koelzer appears to be outlining a defense that the government induced Williams to agree to seek contracts in return for the loan.

Ronald Penque, one-time partner in the company that started the titanium venture, testified that he first learned of the Virginia mine when looking for a source of phosphates to use for recycling garbages. Penque said his partner, Henry A. (Sandy) Williams III, an alleged coconsipirator, who testified against the senator, visited the mine site and found ore sampling containing both phosphate-bearing apatite and titanium-bearing ilmenite.

He added that he knew Sandy Williams was close to the senator, but he said he never heard that the Senator had an interest in the mine.

Another defense witness, New Jersey official Joel Jacobson, contradicted testimony by key government witness Sandy Williams. Jacobson said that the senator never tried to influence a state Public Utility Commission decision on permits for a garbage recycling company in which his wife held an interest. Sandy Williams had testified that the senator did try to influence Jacobson in that decision.

At the end of the day, Koelzer began calling character witnesses, including a priest and a rabbi, to testify that they had the highest opinion of the senator's personal integrity.