PRECIOUS-Gold at 4-week low as dollar firms; investors await Yellen speech

* Markets await Jackson Hole meeting for rates clues
    * Silver, platinum and palladium at multi-week lows
    * Coming up: Fed's Yellen to speak on Friday at 1400 GMT

 (Updates prices; adds comment, second byline, NEW YORK
    By Marcy Nicholson and Jan Harvey
    NEW YORK/LONDON, Aug 24 (Reuters) - Gold dipped 1 percent to
a four-week low on Wednesday as the dollar strengthened and
markets looked ahead to a speech by Federal Reserve Chair Janet
Yellen that will be closely watched for further clues on U.S.
interest rate policy.
    Yellen is scheduled to address a meeting of central bankers
in Jackson Hole, Wyoming, at 10 a.m. EDT (1400 GMT) on Friday.
Recent hawkish comments from Fed policymakers have raised
investors' expectations that she might adopt a less cautious
tone on rates. 
    Rising U.S. interest rates increase the opportunity cost of
holding non-yielding bullion and boost the dollar, in which gold
is priced.
    Dollar strength helped push gold lower on Wednesday.
    Spot gold was down 1 percent at $1,324.66 an ounce by
3:06 p.m. EDT (1906 GMT). 
    U.S. gold futures for December delivery settled down
1.2 percent at $1,329.70, with more than 12,000 contracts
trading within one minute at 8:41 a.m., when the price fell a
steep $9, tumbling below the 50-day moving average.
    "It's all still up to what happens at Jackson Hole," UBS
analyst Joni Teves said. "Up until then, it's very hard to make
a call."
    "Based on market pricing, it seems there is a general
expectation for a December move, so (the statement) would have
to be quite hawkish for markets to bring forward that
expectation to September," she said. 
    According to the CME Group's FedWatch tool, markets are
pricing in a 21 percent chance of a rate increase at the Fed's
September policy meeting, and a 50 percent chance of at least
one rise by the end of the year. The U.S. central bank also has
scheduled policy meetings for November and December.
    "The selling continued and we saw a total of 40,000
contracts in a half-hour period trading down," said Miguel
Perez-Santalla, vice president of Heraeus Metal Management in
New York.
    "The talk is that expectations are that the Fed, after the
Jackson Hole meeting, will come out more hawkish than
    Spot silver fell for the fourth straight session, and
was down 1.2 percent at $18.55 an ounce, after falling to
$18.51, the lowest level since June 30.
    China's silver imports in July fell 36 percent, customs data
showed on Wednesday, while platinum imports were down by nearly
half. Palladium imports rose 17 percent. 
    Platinum was down 1.6 percent at $1,081.40 after
falling below its 50-day moving average to $1,071.20, the lowest
level since July 25. Palladium fell as much as 2.8 percent to
$676.97, also the lowest point since July 25.

 (Additional reporting by Nallur Sethuraman in Bengaluru;
Editing by David Clarke and Paul Simao)