update: some may say there is a third minor third, that in the harmonic series between the 6th and 7th overtones (G to a very flat Bb, overtones of C).   I don’t believe it is used in western music, except in the rarified world of “singing by the ring” barbershop quartet improvisation … correct me if you think otherwise.  It would be a very small minor third, 29 cents flatter than the equal tempered variety; I personally consider it a form of augmented second, but have never argued the matter with anyone.