Faceted Blue Spinel Gemstones, Soviet Gem Stone:Marquise, 13.5x8mm, 4.95ct These latter stones visibly shift

These latter stones visibly shift as you turn them around giving vivid paraiva-like colors

The camera overstates the red vs the eye and struggles to capture the green

The 81g piece measures 37x30x28mm and the 86g piece measures 38x30x29mm

and which color predominates depends on the lighting (color and angle) as well as the background it is set against

with a faceted LuAG Lumogarnet on the front

Faceted Blue Spinel Gemstones, Soviet Gem Stone:Marquise, 13.5x8mm, 4.95ct These latter stones visibly shiftThese are blue gems cut from old stock flame fusion spinel grown in the Soviet Union, sourced from an old collection The color intensity and darkness varies considerably from stone to stone, each is photographed individually. Blue Spinel is typically colored by cobalt, which gives it a red fluorescence with strengh varying based on cobalt concentration and codopant types. While this material is grown with the flame fusion method, in industry