There's two ways of investing in gold: buying actual pieces of gold, and buying stock in gold mines, either actual stock or mutual funds. Both are hedges against the rise and fall of the stock market and stock crashes. Here's my opinion on the issue.
Investing in gold mines by purchasing stock is a great and easy way to diversify your portfolio and protect yourself somewhat from an economic collapse THAT LEAVES THE STOCK MARKET/FINANCIAL SYSTEM INTACT AND WORKING. If the organic fertilizer really impacts the impellers hard, and the whole system fails, you've lost everything because your stocks and mutual funds have just turned into fancy firestarters.
Purchasing actual pieces of gold is both a hedge against minor economic collapse as well as a complete failure of our economic system. Remember that our economic system is based upon nothing more than everyone's belief in the stability of the government and that ought to frighten you. Anyway, the problem is, it's a lot more time and energy intensive to purchase gold and silver and then you have to store it somewhere.
What I am doing (very slowly, unfortunately) is collecting gold and silver coins that have no historic/collectible value. Stay away from Morgan Silver Dollars and the such; get foreign coins that sell for whatever the going rate is for that weight of gold or silver at coin shops. If it ever comes to it, at that point, one troy ounce of silver will be worth whatever it's worth, regardless of whether it's in some foreign coin so beat up you can't tell its origin or a perfect condition Morgan Silver Dollar you paid through the nose for.