(MONEY Magazine) – Most experts were caught off guard by the recent explosive rise in gold-mining shares. The investors who scored -- with gains of up to 100% -- were those prescient few who bought mining stocks late last year when gold was in the dumps (for the current gold outlook, see page 43). There's a lesson in that: When gold and other commodities start to move, they can shoot up so fast that you miss the chance for big profits. So it's smart to buy top-quality mining shares when the newspapers are telling you that metals prices are deeply depressed. Such an opportunity may be shaping up right now for buyers of Phelps Dodge (ticker symbol: PD; NYSE, $45.50), the largest U.S. copper-mining company, with estimated 1993 revenues of $2.8 billion.

Copper prices recently sank to less than 80 cents a pound, their lowest levels in 5 1/2 years. Moreover, analysts say that if, as expected, the U.S. economy avoids slipping back into a recession, copper prices could top $1 a pound in '94 and hit $1.20 in '95. If that happens, Phelps Dodge's earnings will soar. ''Every 1 cents increase in the price of copper is worth more than a dime of earnings a share,'' says metals and mining analyst Vahid Fathi at Kemper Securities in Chicago. He thinks the stock could rise 32% to $60 a share within 12 months. Analyst Peter Anker at NatWest Securities in New York City also likes the stock and sees a $65 price in 16 months. Yet a number of metals analysts rate the stock as merely a hold. How come? Because copper prices could weaken during the summer as manufacturing slows for vacation season in Europe, and Phelps Dodge stock could dip 10% to below $41. ''I'd buy the stock at a cheaper price,'' says analyst J. Clarence Morrison at Prudential Securities. He notes that the company has five new mines that could triple net income in 10 years. Echoes analyst Thomas Van Leeuwen at First Boston in New York City: ''I like the company, but I think there will be a better buying opportunity this summer.'' It's your call whether to buy the stock now and collect its 3.6% yield or wait and try to catch a better price. What would I do? Well, I bought gold stocks nine months too early, sold them too soon and still made a terrific profit. But then, I've always been a lousy trader.