Each point x in Gr ( r , n ) corresponds to an × matrix A which gives rise a matroid M on its columns. Gel'fand, Goresky, MacPherson, and Serganova showed that the sets { y ? | = } form stratification of with many beautiful properties. However, results Mnëv Sturmfels show these strata can be quite complicated, particular may have arbitrary singularities. We study ideals I varieties, Zariski clo...