* Gold, silver fall sharply for third straight day
* Sentiment down after George Soros sold gold, silver
* Bullion market ignores news of Mexico gold accumulation
* Coming up: U.S. April nonfarm payrolls due Friday (Recasts, updates market activity, adds comment, link to graphic)
By Frank Tang
NEW YORK, May 4 (Reuters) - A 5-percent tumble in silver on Wednesday marked its biggest three-day loss in five years, and dragged gold down, as speculators continued to dump long positions after margins requirements were hiked early this week.
Silver has now lost 20 percent, the conventional criteria for a bear market, since it rallied to a record high near $50 an ounce last Thursday. Gold also notched its worst three-day decline since January despite a broad dollar drop and a ramping up of gold reserves by Mexico.
Despite a sharp pullback, silver is still one of the top-performing commodities of the year with a 30 percent gain.
But investors remained wary of a market in almost chronic surplus and a highly volatile price.
Sentiment among precious metals investors also took a hit after a report said high-profile investor George Soros, who was bullish on gold and a top investor in gold funds, has been selling gold and silver in the past month or so.
"With the CME raising three times in a week the margin requirement of silver, that was enough to disrupt the parabolic move in silver prices," said Mark Luschini, chief investment strategist of broker-dealer Janney Montgomery Scott, which manages $53 billion in client assets.
Spot silver
Technicals were in focus after silver broke below its 20-day moving average on Tuesday, which had held since February. But prices were still well above the 100- and 200-day averages, after a 170 percent rally over the last 12 months.
Silver's decline sent the gold/silver ratio to a three-week high near 40 from just below 32 last Thursday.
Spot gold
COMEX June gold futures
Holdings of the largest gold-backed exchange-traded-fund
(ETF), New York's SPDR Gold Trust
Also factoring into gold was news that George Soros' big $28 billion firm and some hedge funds have been selling gold and silver, while other notable managers including John Paulson continued to favor precious metals, the Wall Street Journal reported, citing sources.
In the third quarter of 2010, Soros reduced some of his big bets on gold, a market he has called "the ultimate bubble." [ID:nN15263362]
The bullion market largely ignored news that Mexico's central bank has beefed up their bullion reserves by buying over 90 tonnes of gold, more than $4 billion worth, over the past couple of years to put some of their massive foreign exchange holdings to work. [ID:nLDE7431OZ]
"The size (of the purchase) is certainly pretty chunky to have been accomplished in that space of time. So it certainly gives another sizable layer of support to gold's position in the international reserves system," said Credit Suisse precious metals analyst Tom Kendall.
Platinum
SETTLE CHNG CHNG VOL US Gold JUN 1515.30 -25.10 -1.6 1505.50 1543.50 223,051 US Silver JUL 39.388 -3.197 -7.5 38.940 42.325 146,614 US Plat JUL 1826.30 -34.20 -1.8 1816.70 1859.10 4,999 US Pall JUN 746.70 -35.70 -4.6 741.60 779.55 5,636 Gold 1515.94 -24.44 -1.6 1506.86 1542.96 Silver 39.580 -2.060 -4.9 39.000 42.300 Platinum 1819.74 -33.57 -1.8 1818.00 1854.00 Palladium 742.05 -41.64 -5.3 745.00 775.72 TOTAL MARKET VOLUME 30-D ATM VOLATILITY
CURRENT 30D AVG 250D AVG CURRENT CHG US Gold 235,296 176,523 18.51 1.06 US Silver 162,476 66,926 49.65 4.80 US Platinum 5,082 7,857 21 1.00 US Palladium 5,834 4,519 (Additional reporting by Marie-Louise Gumuchian in London and Rujun Shen in Singapore; editing by Alden Bentley)