The problem historically with using gold as money is that it was combined with fractional reserve banking. This meant that banks printed up more receipts for gold than they had in the vault (same thing they do today with the $US and fractional reserve lending). This causes the boom and bust business cycle of inflation and deflation. It doesn’t mean gold is changing value.
www.mises.org/books/desoto.pdf
This book does a great job of summarizing 500 years of world banking history. It is interesting to see that the same problems recur over and over each generation.