Shares of Tiffany & Co. (TIF - Get Report) have been on fire, roaring higher by more than 20% in 2017 and climbing 47% over the past 12 months. Investors hope the momentum will continue when Tiffany reports earnings on Wednesday before the bell.

Analysts from Jefferies and Cowen recently came out with research reports essentially saying that diamonds haven't lost their luster, TheStreet's Jim Cramer, manager of the Action Alerts PLUS portfolio, said from the floor of the New York Stock Exchange Tuesday.

Cramer agrees that the diamond business remains strong and said that Tiffany operates a very good supply chain. Tiffany is an "up-stock" right now, he added; meaning, it's in a solid up-trend.

The weaker dollar is also helping business, Cramer noted.

"I think Tiffany will be very good," he reasoned. If the stock goes down, investors should strongly consider buying it, he concluded.

Analysts expect Tiffany to earn 70 cents per share on $913.44 million in revenue for the most recent quarter.

At the time of publication, Cramer's Action Alerts PLUS had no position in any companies mentioned.