From the tip of the Baja Peninsula in Mexico, Mammilaria schumanni is a pretty blue bodied, clumping, globular cacti with stems to 2 inches around. It gets large purplish pink flowers in summer. It has hard very sharp white spines with black tips and offsets like mad.
     I liked the contrast of the white spines with black tips against the blue green body. I intend to take the pups from this one and then repot it. I have another single stemmed one that goes in the garden.