1. Two 110 ct. faceted tanzanite drops with an estimated retail value of up to $300,000. Also look for pairs of 10–60 ct. stones and perfectly matched emerald ­layouts. A G Color, New York City; 212-207-3905; agcolor.com

2. Black and brown diamond bead strands of varying lengths (3 mm–3.5 mm, $400; 2.5 mm–3 mm, $350). Taj Co., New York City; 800-325-0825; tajco.com

3. One-of-a-kind South Seas pearl jewels, like a flower ring in 18k gold with two natural keshi weighing 5.3 grams and 1.05 cts. t.w. diamonds (retail: $8,400). Emiko Pearls International, Bellevue, Wash.; 425-646-0111; emikopearls.com

4. Sapphires in any color—especially natural, untreated ones—and blue gems across the board: 6.73 ct. oval-cut sapphire in platinum with 0.52 ct. t.w. ­diamonds (retail: $32,000). Omi Gems, Los Angeles; 877-664-4367; omigems.com

5. Look for Chinese freshwater pearls like these bead-nucleated Fireball pearls (11 mm–18 mm, from $250 a strand); Sea Hunt Pearls, San Francisco; 415-543-7900; seahuntprl@aol.com