Those are crocus tommasinianus, usually the first crocuses to appear in late winter, very early spring.  The common form is lavender, but there are cultivars of white, and many variations on purple with or without white markings. They are self-seeding and there's no telling where they may turn up in your garden after a few years.

These crocus are hardy corms that grow in zones 3 to 8, in conditions of sun or light shade. They usually bloom in March and are a very welcome sight as winter comes to an end.

Courtesy of NYBG Plant Information