Blue Nile (Nasdaq: NILE) is starting to show its age. The online jeweler kicked off 2008 in ho-hum fashion, with net sales climbing just 4% to $70.5 million. Net income fell to $0.16 a diluted share, after earning $0.19 a share a year earlier.

The turn for the worse has been swift, since the company was growing just fine three months ago.

The dip in profitability doesn't indicate that Blue Nile's days as a growth stock are numbered. The company posted lower quarterly earnings on a per-share basis twice in 2006. The real concern is the top line. If not for a 124% spike in international sales, Blue Nile's top line would have actually declined during the quarter.

The stateside slowdown is troublesome. Blue Nile faults general economic trends, but that isn't true of all online jewelry sellers. (Nasdaq: BIDZ), which uses an auction format to move its wares, posted top and bottom line gains of 39% and 34% respectively during the same quarter. (Nasdaq: AMZN) and (Nasdaq: OSTK) don't break down their jewelry sales, yet Amazon's net sales surged 37%, with Overstock's total revenue jumping by 27%.

Physical retailers like Tiffany (NYSE: TIF), Signet (NYSE: SIG), and Zale (NYSE: ZLC) may post lackluster reports over the coming weeks, but Blue Nile is priced more like a dot-com than a conventional jeweler.

Blue Nile's blazing start after its 2004 IPO drew David Gardner into selecting the engagement ring specialist as his first pick in the Rule Breakers newsletter. The stock has beaten the market since then, soaring 54% , though Blue Nile was trading much higher when it peaked at $106.16 last September.

If 2006 taught us anything, it's that Blue Nile knows how to get back on the horse again after falling off. The real question now is whether Blue Nile will still sit tall in the saddle once the economic doldrums leave town.

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Longtime Fool contributor Rick Munarriz proposed to his eventual wife 19 years ago. Alas, there was no commercial Internet around at the time. He does not own shares in any of the companies mentioned in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.