If I let myself, I become upset and a bit terrified by smooth hard structures. A good example is the most perfect sphere in the world, seen here. It's a polished sphere of solid silicon-28.
The metal cylinder held by the host later in the video also creeps me out.
A sphere of smooth concrete, granite, marble, or some other hard substance is the worst.
What's the best prefix for my -phobia?
(I think the reason for this phobia is that I slipped and whacked the back of my head against a smooth concrete surface when I was very young.)