Do me a favor and look at how many CME Notices were issued raising margin requirements for precious metals in the past year. Hint: They do this all the time to account for market volatility and the contract value. If a contract increases by 10% margin is not static. CME raised margin requirements several times in the last month to little market effect.

Silver crashed because China halted trading on the only public silver and gold ETFs Friday. There are videos of HK police arresting guys freaking out because they couldn't cash out beforehand: Apparently the fund had been operating as some kind of pyramid scheme and was not solvent at those prices.

Also on Friday, China urged investors to "invest responsibly" or some such (source: FT) and froze a bunch of suspicious accounts. I believe those accounts were behind the pump and dump social media ("AI Asian Guy" videos on Youtube, investment subreddit spam) with the help of plenty of useful idiots.

There's a ton of good coverage of the precious metals run up in FT this past week.