Sales for jewelry categories such as diamonds and fashion jewelry delivered some modest gains for Blue Nile Inc. in 2012, but what really drove growth was a nice spike in international sales and its core business of engagement rings.

For the year ended Dec. 30, Blue Nile, No. 71 in the 2012 Internet Retailer Top 500 reported:

• Total sales increased year over year 14.9% to $400 million from $348 million.
• Net income declined 26.3% to $8.4 million in 2012 from $11.4 million in 2011.
• Sales of engagement rings grew year over year 21.7% to $226.6 million from $186.2 million.
• Sales in other jewelry categories increased 4.8% to $111.0 million in 2012 from $105.9 million in 2011.
• International sales grew year over year 11.6% to $62.4 million from $55.9 million.

“In our core U.S. engagement business, we hit all of the key milestones we set for ourselves at the beginning of the year,” CEO Harvey Kanter told Wall Street analysts on the company’s year-end earnings call. “Our engagement business had the highest level of growth in five years.”

For the fourth quarter:

• Total sales increased year over year 21.2% to $136.1 million from $112.3 million.
• Net income increased 16.7% to $4.9 million in 2012 from $4.2 million in 2011.
• Sales of engagement rings grew year over year 31.0% to $73.6 million from $56.2 million.
• Sales in other jewelry categories increased 5.2% to $42.5 million in 2012 from $40.4 million in 2011.
• International sales grew year over year 27.4% to $20.0 million from $15.7 million.

In 2012 as many as 40,000 customers shopped for an engagement ring or traded up for a more expensive ring, Kanter told analysts. Blue Nile’s inventory now includes more than 150,000 loose diamonds. Mobile commerce also is playing a bigger role in Blue Nile’s ongoing e-commerce business. “In the fourth quarter of 2012, one-third of our visitors to our store came from a mobile device,” Kanter told analysts. “Total visitors for mobile devices grew by over 40% from the prior year and we believe this will be over half of the visitors in 2013.”

With a growing base of international sales, Blue Nile also is looking to expand in China. In 2012 Blue Nile acquired an undisclosed stake in an unnamed jeweler in order to fulfill orders for engagement rings in China. The retailer also has a deal in the works with Show.com, a Chinese marketplace company, to sell other types of jewelry. “Our investments in China are in early stage, but beginning to impact the business,” Kanter told analysts.