Name the movie: A group of westeners goes into the jungle in Borneo, looking for diamonds.?

The group is lead by an ex-army guy. He talks to a local for help, who goes on to tell his father, I think, who is leader of a tribe and has a large diamond hanging from his neck, as proof that there are diamonds. The group and the tribe collides in battle, and in the end the leader of the tribe looses his diamond. The group leader returns to his solitude in a small house, and the female leading actress is seen driving away after she speaks to him in the house about a book, or being civilized or something, not sure can't remember exactly. I think the movie is made in the 1980-90's. Do you know the title?