* S&P 500 on track to end June lower, but positive for quarter
* Accenture and BlackBerry both tumble after results
* Molycorp climbs after SEC investigation ends
* Dow down 0.4 pct, S&P 500 off 0.1 pct, Nasdaq up 0.1 pct
By Ryan Vlastelica
NEW YORK, June 28 (Reuters) - U.S. stocks edged mostly lower in a volatile session on Friday, with investors finding little reason to push shares higher after a three-day rally.
Shares fluctuated between steep losses and modest gains, trading flat for much of the session before pulling back. Technology shares were among the weakest of the day, pressured by weak corporate results, but the losses were partially offset by strength in energy and material shares.
Cyclical groups, which include materials and are tied to the pace of economic growth, have rallied this week on receding concerns that the Federal Reserve's stimulus program - widely credited with fueling the market's gains this year - would end soon.
Last week, Fed Chairman Ben Bernanke suggested the policy could be slowed if the economy improves, resulting in a selloff of nearly 5 percent, though that subsequently dissolved on signs that the end of the stimulus program wasn't imminent.
On the last trading day of June, both the S&P 500 and Nasdaq are on track to end a seven-month rally, while the Dow is set to end a six-month surge.
"The market is continuing to adjust as we try and figure out what's going on with respect to Fed policy, and we should continue to see volatility as things get sorted out," said Rex Macey, who helps oversee $20 billion in assets as chief investment officer of Wilmington Trust in Atlanta.
"We're cooling off a little bit after a few days of strong action," Macey added.
For the month of June, the Dow is down 1 percent, the S&P 500 is down 1.3 percent and the Nasdaq is down 1.6 percent.
An S&P index of technology shares fell 0.5 percent on Friday and ranked as one of the worst-performing S&P sectors.
Accenture PLC tumbled 10.8 percent to $71.55,making it the biggest drag on the S&P 500 after the company cut its full-year outlook. The results also put a dent in shares of competitor IBM, which dropped 2.8 percent to $190.16. IBM was the biggest weight on the Dow.
Energy and material shares advanced, with Newmont Mining up 7 percent at $29.65 and Nextera Energy up 1.5 percent at $81.66.
The Dow Jones industrial average was down 52.11 points, or 0.35 percent, at 14,972.38. The Standard & Poor's 500 Index was down 1.41 points, or 0.09 percent, at 1,611.79. The Nasdaq Composite Index was up 4.66 points, or 0.14 percent, at 3,406.52.
The S&P 500 has climbed 2.6 percent over the previous three sessions as economic data and comments from U.S. Federal Reserve officials soothed worries about an earlier-than-expected pullback of the Fed's stimulative bond purchases.
For the week, the S&P 500 is up 1.1 percent, ending a two-week string of declines.
The Dow is up 1.2 percent for the week, while the Nasdaq is up 1.4 percent.
For the second quarter, the Dow is up 2.7 percent, the S&P 500 is up 2.6 percent and the Nasdaq is up 4.1 percent.
Newmont Mining was the S&P 500's weakest performer in the second quarter, down 34 percent, while First Solar was the strongest, jumping 65 percent.
Friday's economic data showed that consumer optimism remained high in June. The Thomson Reuters/University of Michigan's final reading for June on the overall index on consumer sentiment was 84.1 points, slightly below a near six-year high of 84.5 in May. Economists polled by Reuters had forecast a final June reading of 82.8.
But a closely watched gauge showed that manufacturing activity declined in the Midwest this month. The Chicago Purchasing Manager Index fell in June to 51.6, below expectations.
U.S.-listed shares of Research in Motion plunged 25.6 percent to $10.78 after the BlackBerry maker offered few signs of a long-promised turnaround on Friday. It reported an unexpected quarterly operating loss, a dearth of details on sales of its make-or-break new line of devices and no return to profit expected in the current quarter.
Molycorp Inc jumped 8 percent to $6.06 after the rare earths producer said the U.S. Securities and Exchange Commission completed an investigation into the company and didn't recommend enforcement action.
Arch Coal Inc gained 4.7 percent to $3.77 after the company agreed to sell its Canyon Fuel subsidiary for $435 million in cash.
Investors can expect a surge of volume at the close on Friday when Russell Investments is expected to set the final update for the annual reconstitution of its indexes.