Jewelers International Showcase brings the heat to the Miami Beach Convention Center April 9–11.   (Top) Wisdom necklace in 18k gold vermeil with turquoise; $1,495; Nina Nguyen Designs, Lafayette, Colo.; 720-459-7664; nina-nguyen.com   (Inset) Ring in silver with 18k gold beads; $169; Samuel B. Collection, Great Neck, N.Y.; 516-466-1826; samuelb.com   Earrings in 14k gold with black rhodium and 7.74 cts. t.w. diamonds; $8,010; MK Diamonds, Los Angeles; 800-624-2634; mkdiamonds.com   Ring in 18k gold with 7.68 cts. t.w. diamonds; $11,800; Shy Creation, Los Angeles; 213-623-8900; shycreation.com   Snowflake bracelet in 18k white gold with 7.21 cts. t.w. diamonds; $41,915; Yael Designs, San Francisco; 415-989-9235; yaeldesigns.com