We may receive commissions from some links to products on this page. Promotions are subject to availability and retailer terms. That precious metal market volatility isn't just random noise, though.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com. What is rust? – Henry E., age 13, Boston, ...