A specific crystalline order, involving the Fibonacci series, had until now only been observed in plants (phyllotaxis). Here, these patterns are obtained both in a physics laboratory experiment and in a numerical simulation. They arise from self-organization in an iterative process. They are selected depending on only one parameter describing the successive appearance of new elements, and on initial conditions. The ordering is explained as due to the system's trend to avoid rational (periodic) organization, thus leading to a convergence towards the golden mean.