Blue Nile's stock surged more than 20 percent Thursday after the Seattle Internet jeweler posted second-quarter sales that beat Wall Street estimates.

Blue Nile said its sales rose 13 percent from a year ago to $91 million, exceeding analysts' forecast of $88.8 million.

The company also said it expects its third-quarter sales will range from $87 million to $91 million, above the $84.7 million predicted on Wall Street.

But Blue Nile reported a 44 percent drop in its second-quarter profit, suggesting a post-recessionary turnaround is far from complete.

The company saw a profit of $1.6 million, or 11 cents a share, compared with $2.8 million a year ago.

An improved market for diamond engagement rings proved key as Blue Nile posted $52.4 million in related sales during the quarter, up from $43.9 million a year ago.

Blue Nile's stock climbed $5.25, or 22.1 percent, to $29 in after-hours trading Thursday following the earnings report. The stock closed the regular trading session down 40 cents, or 1.7 percent, at $23.75.

Amy Martinez: 206-464-2923 or amartinez@seattletimes.com