A millionaire retired chemist was sentenced in federal court in Philadelphia today for stealing a mammoth ivory tusk from government property in Alaska.

Robert Franz, of Plymouth Meeting, was fined $100,000, put on probation for three years and ordered to perform 300 hours of community service by U.S. District Judge Berle M. Schiller.

Prosecutors said Franz, a retired medical chemist who worked for GlaxoSmithKline and its predecessors for 32 years, stole the tusk in June 2007 from the U.S. Bureau of Land Management on the north slope of Alaska in the Arctic National Wildlife Refuge.

Franz, 65, pleaded guilty in November to conspiracy to defraud the United States and theft of government property.

Assistant U.S. Attorney Alicia M. Friend said that while the case "may conjure images of Indiana Jones," Franz was just a thief and an "artifact hunter" who "used his wealth to gain access to protected lands, and then willfully pillage artifacts and natural resources . . ." with an outfitter and tour guide, Karen Jettmar.

Jettmar was recently indicted in Alaska on similar charges.

Prosecutors said the two exchanged e-mails in late 2007 including statements that Franz's tusk was "safe in Pennsylvania" from the bureau.

Court papers said Franz, who is worth more than $3 million according to the feds, told an undercover federal agent on a 2009 trip on the Utukok River in Alaska that the tusk was valued at between $8,000 and $12,000. (A qualified appraiser put the value at $4,000 at the time Franz removed it from public land, prosecutors said.)

Friend, who said "greed" and "eccentric need" were Franz's motivating factors, had sought a sentence of 14 months in federal prison.

But defense attorney Richard Hark said his client was an avid hiker who had been to the Alaskan wilderness area many times.

On one occasion, Hark said, Franz found a tusk laying on a river bank which Franz admitted was "too good to pass up."

Hark said Franz mailed the tusk to his home and put it in an armoire in his home for personal enjoyment and never sold it.

In an unrelated matter, Franz was charged in January with possession and receipt of child porn. He has pleaded not guilty and is presently awaiting trial.

Contact Michael Hinkelman at 215-854-2656 or hinkelm@phillynews.com, or follow him on Twitter @MHinkelman.