Gentianella Campestris - small clusters of mauve flowers. (Small white flowers around it are Eyebright)

It's normally accepted that Field Gentian has 4 petals and German (or Chiltern) Gentian has 5 - but I've seem plants with both occurring quite naturally in the French Alps.

Found below Col de la Croix du Bonhomme, Tour du Mont Blanc, France July 2011