UPDATE 2-Reliance Steel's quarterly profit plummets

* Q3 EPS 57 cents v Street estimate 46 cents

* Revenue drops more than half

* Stock down 4.2 pct (Updates with analyst comment, stock drops)

NEW YORK, Oct 22 (Reuters) - Metals processor Reliance Steel & Aluminum Co (RS.N) said on Thursday that third-quarter profit fell, due in part to lower prices and volumes.

But although its earnings were better than Wall Street expected, the company's stock fell 4.2 percent to $41.84 a share in midday trading on the New York Stock Exchange.

"Although third-quarter earnings were much higher than expected, the company ... decided not to provide a quantitative forecast for the fourth quarter due to uncertain business conditions," said independent analyst Michelle Applebaum, of Steel Market Intelligence in Chicago.

She noted in a research note that Reliance believes "there may be some slight downward pressure on pricing for many of their products in the coming months."

Net earnings were $41.8 million, or 57 cents per share, compared with $152.5 million, or $2.07 per share in the same quarter of last year, the Los Angeles-based company said.

Revenue fell by more than half to $1.24 billion from $2.57 billion a year earlier.

Analysts on average were expecting earnings of 46 cents, according to Thomson Reuters I/B/E/S.

Last month, Reliance said earnings would be in the range of 40 cents to 45 cents per share due to prices and profit margins increasing in the third quarter over the second.

(Reporting by Steve James, editing by Dave Zimmerman and Gunna Dickson)