This is a common species in much of Europe, flying in a single brood from April or May to August in flowery places where its foodplant, red clover, grows.

The male is a rather steely blue when fresh, with variably broad, dark borders and dark etching along the lines of the veins. Occasionally there is dark suffusion over the wings but more typically they are clear and bright. The female is all brown above without orange lunules, though in Greece there are subspecies, including ssp. helenus, which do have orange on the hindwings and sometimes the forewings too. The underside of the male is grey with arcs of postdiscal spots but no submarginal markings. The female is similar but a deeper brown colour. Again, there are orange spots near the anal angle of the hindwing in some Balkan subspecies. Confusion is possible with the Osiris blue. The male Osiris blue has a narrower marginal border on the upperside and clearer wings but the female is superficially very similar. It is useful to note the three uppermost spots in the postdiscal series of the underside hindwing. In the mazarine blue these are aligned in a broadly obtuse angle - more than 130°. In Osiris blue the angle is typically closer to a right angle and always less than 120°.

Eggs are laid on flowers of red clover, where the caterpillars feed prior to hibernation. After hibernation they feed on the fresh leaves. The caterpillars have a relationship with ants.