Is it considered Fornication if you you have with someone you were once married to, but divorced?

Technically their not married, neither one, but they were each others last partner, they have been living apart for years, idk if legally separated but they have been physically and intentfully separated, and opened to the fact. In the realm of Islam intent is fact, so in this situation they are rightfully separated. It doesn't matter if they can jip the system and say their married on whatever they can in order to benefit in the United States, if your not "married", your not "married".Any Qu-ranic Studies majors that would know what the Qu-ran says about Fornication with your Wife after a divorce or even in the mist of a serious divorce?????