Here's a ring to keep everyone guessing.  It's set with a 1.26ct red spinel to the centre of a diamond cluster.
 
The spinel is an oval-shaped mix cut held in four white claws with a rub-over set baguette cut diamond to each side and with an arch of five claw set diamonds above and below to a white shaped cluster mount.  Rectangular profile yellow shoulders to a D-shaped yellow band.  The band doesn't have a hallmark but is stamped "18CT PLAT" and tests as 18ct gold with platinum.
 
Details:
 
Red spinel:
Measures 7.90mm x 5.90mm x 3.58mm
1.26ct
Stong pinkish colour, minimal inclusions
 
Diamonds:
Baguette cut diamonds - measure 3.90mm x 1.90mm
Brilliant cut diamonds - measure 2.20mm diameter
Total carat weight: 0.60ct
Assessed colour: F-H,
Asessed clarity: VS-SI
 
Cluster Head: 13.30mm x 11.10mm
Finger size: O (UK/Australia); 7 (US/Canada)