Hong Kong, Jan. 12 -- Emma Stone has one, Michelle Williams has one, and now, so doesAriana Grande.We're talking about pearl engagement rings, the most unexpected wedding jewellery trend to have emerged in the past year.

Of course, we've been seeing pearls everywhere for a while now. The organic gem is very much in fashion, especially those of the misshaped, freshwater variety. We've seen them strung on necklaces or dangling from earringson the runwaysofGucci,Givenchy,Jil Sander, Simone Rocha - just to name a few.

Even men are wearing them. Comme des Garcons' Rei Kawakubo, having noticed that they look good in them,launcheda unisex pearl collection with Japanese jeweller Mikimoto this year as well.

"The pearl is very classic, but it is...