CAMBRIDGE, Mass. (AP) -- Benoit Mandelbrot, a well-known mathematician who was largely responsible for developing the field of fractal geometry, has died. He was 85.

His wife, Aliette, says he died Thursday of pancreatic cancer. He had lived in Cambridge, Mass.

The Polish-born French mathematician founded the field of fractal geometry, the first broad attempt to quantitatively investigate the notion of roughness. He was interested in both the development and application of fractals, which he also showed could be used elsewhere in nature.

For years, he worked for IBM in New York. Later he became Sterling Professor Emeritus of Mathematical Sciences at Yale University.