Turquoise turns up in jewelry designers’ summer collections as sure as tulips in the spring. Found in shades ranging from Tiffany blue to lime green, the gem is a favorite for the tropical-water imagery it evokes. And with the closure of the Sleeping Beauty mine in Arizona, availability of quality goods is poised to plummet while prices are set to skyrocket. If you like those azure rocks, stock up now or live in regret forever.  Earrings with 11 cts. t.w. diamonds, 2 cts. t.w. sapphires, 22 cts. t.w. turquoise in 18k rose gold; $29,000; Sutra, Houston; 713-984-4987; sutrajewels.com18k gold and diamond Chinese turquoise brooch; $9,770; Barbara Heinrich Studio, Pittsford, N.Y.; 585-383-1089; barbaraheinrichstudio.comLupita ring in 18k white gold, with Sleeping Beauty turquoise and 2.51 cts. t.w. colorless diamonds; $16,000; Carla Amorim, Chicago; 312-305-6476; carlaam