Metal market periodicity

I was thinking about the current rise of gold and silver prices and trying to figure out an apparent cause, when I looked at a 2 year graph and stumbled upon this interesting thing:

 

There seems to be a 6 month cycle of sudden rises and subsequent slow drops, like teeth on a saw blade, and the “blade” has a 20° incline, approximately. This means that the current events have very little to do with the pattern, as tempting it may be for one to grasp at them, looking for explanations. I don’t have an explanation for the 6 months cycle, but if I had to guess, it might have something to do with financial cycles I’m not aware of.