GLOBAL MARKETS-Stocks slide as economic optimism tempered

* European shares fall 1.2 percent; world stocks ease 0.6 pct

* Emerging markets ease as rising volatility hits risk taking

* Oil prices fall below $70 a barrel as dollar rises

* Dollar firms as BRICs come up with no new initiatives

By Sujata Rao and Mike Dolan

LONDON, June 17 (Reuters) - World stocks slid for the fourth day on Wednesday as investors grew sceptical that the speed of the global economic recovery would match the sort of financial market optimism that has fuelled a 40 percent rally in the second quarter so far.

Mining stocks led the losses in Europe as commodity prices .CRB also showed some reversal.

Doubts about the heralded global economic recovery are starting to weigh on sentiment everywhere after some U.S. economic indicators this week came in below expectations, raising fears that investors may have pushed up equity and commodity prices too quickly.

Stock corrections have been relatively tame so far but they have taken world stocks .MIWD00000PUS as well as emerging equities .MSCIEF down to three-week lows.

"We've had a very good run from the March lows. The market was losing momentum and getting ready for some form of correction," said Bernard McAlinden, strategist at NCB Sctockbrokers.

A positive investor sentiment reading on Tuesday in Europe's biggest economy, Germany, was overshadowed by poor industrial output data in the United States and disappointing sales by top U.S. retailer Best Buy which spurred worries about an anaemic recovery and pushed Wall Street down over one percent.

"We seem to be stuck in a negative mode now, and we're well down on levels seen last week," said Peter Dixon, economist at Commerzbank. "Some of the hype on the recovery seems to have faded and we seem to be returning to realism."

By 1130 GMT, the pan-European FTSEurofirst 300 .FTEU3 was down 1.3 percent, with miners such as Anglo American (AAL.L) and Rio Tinto (RIO.L) leading the losses. Spanish utility Iberdola (IBE.MC) and British grocer J.Sainsbury, both of which announced share issue plans, also fell.

The Reuters-Jefferies CRB index .CRB, a basket of 19 commodity futures, eased further, having slipped about 4 percent from a seven-month high reached last Thursday.

It is still up 15 percent since the end of April.

Wall Street's VIX volatility index -- a measure of risk -- has risen to a three-week high .VIX above 30. Although the backup in the VIX is partly related to a series of options expiries this week, rising volatility will dampen demand for relatively risky assets such as equity and emerging markets in particular. Oil CLc1 ebbed about one percent on Wednesday to below $70 per barrel as the dollar steadied following recent losses -- partly on concern about a fresh equity market nosedive.

DOLLAR

The dollar steadied after emerging BRICs nations -- Brazil, Russia, India and China -- meeting on Tuesday failed to outline any new initiatives on a new reserve currency and as investors returned to dollars from riskier currencies.

By 1130 GMT, the euro EUR= was down slightly at $1.3840. The dollar index .DXY was up 0.2 percent.

"There's been a bit of unwinding in risk due to the slide in equities," said Paul Robson, strategist at RBS.

(Additional reporting by Simon Falush, Naomi Tajitsu, Harpreet Bhal in London, Kevin Plumberg in Tokyo; Editing by Victoria Main)