By Chelsea Emery

NEW YORK (Reuters) - Harsco Corp (HSC.N: Quote, Profile, Research) posted better-than-expected quarterly earnings on Tuesday as strong sales at its minerals and rail services group more than offset the impact of higher fuel costs on its mill services segment.

But Harsco shares were lower on concern that organic revenue growth was slowing and that the mill services group could see continuing weakness, according to Standard & Poor's equity analyst Kevin Kirkeby.

The shares were down $1.89, or 3 percent, at $60.40 in afternoon trading on the New York Stock Exchange.

Harsco, which provides products and services for nonresidential construction and metals producers, said first-quarter profit from continuing operations rose to $56.9 million, or 67 cents per share, from $45.4 million, or 54 cents per share, a year earlier.

Sales climbed 18 percent to $987.8 million, boosted by foreign currency translation.

Analysts surveyed by Reuters Estimates had expected the Harrisburg, Pennsylvania-based company to earn 62 cents per share on sales of $965.8 million.

Kirkeby said the first-quarter sales growth, excluding acquisitions and currency impact, slipped to 7 percent from 9.4 percent in the year-ago quarter.

In addition, "people were looking for an upturn in mill services and we didn't really get the traction people had expected," he said.