Gold prices found support at their key 50-day moving average line as the stock market weakened more Monday after Caterpillar (CAT) cut its 2012 outlook for the second time this year. The blue-chip, heavy-equipment maker said the global economy was slowing faster than it had expected. Spot gold prices added 0.31% to $1,726.80 an ounce. PowerShares DB U.S. Dollar Index Bullish (UUP), which tends to move opposite the yellow metal, was flat at 21.81.