At the AGTA GemFair, taking place Feb. 2–7 at the Tucson Convention Center, the desert flowers won’t be the only beauties vying for attention.   Rectangular tourmaline plates weighing 124 grams; $9,300; Robert Bentley, NYC; 212-302-4846; robertbentleygemstones.com (pictured, top)   Bracelet in 18k gold with sapphires and diamonds; $26,000; Akiva Gil, NYC; 800-592-0009; akivagil.com (pictured, inset)   Round-shape 43.48 ct. ametrine; $4,782; John Dyer & Co., Edina, Minn.; 715-830-0126; johndyergems.com   Ring in 18k gold with 3.01 ct. cushion-shape fancy light yellow diamond, 1.41 cts. t.w. fancy yellow diamonds, and colorless diamonds; $27,800; Tamir, Beverly Hills, Calif.; 310-858-6600; tamirjewels.com     Montauk necklace in 18k gold with 17 mm–22 mm freshwater