Found in only one single valley in Nuevo Leon Mexico, Aztekium ritteri is one of the rarest of cacti. It has very special cultivation requirements and so is more often grafted than not, though I have seen pictures of beautiful specimens on their own roots. In the wild it grows on vertical cliff faces made mostly or limestone or gypsum. So in cultivation some limestone or gypsum in the potting mix is essential (When on it's own roots). It is a small cactus, rarely exceeding 2 inches in diameter, but in time offsets form producing small clumps. The tiny golden spines are only seen on the newer growth. They eventually drop off as the plant ages. The crown eventually becomes wooly and from this pseudo-cephalium the flowers arise. The white or pink flowers are very tiny, less than a half inch, but still can be showy as there may be as many as six open at a time. My specimen is of course grafted and I so hate the look of grafted cacti. I hope some day this one will give me offsets, I really want to try growing some naturally.
     Update September 2nd 2006, I finally have a flower. There were two buds. Unfortunately only one opened and the other fizzled. But more are on the way. Hopefully I'll be able to achieve the display mentioned above.

Closeup showing new growth in June	Even closer	Wooly in July	First flower in September
A closer view	Even closer	Opened further the next day	Two more a week later
A closer view