Old Mine Cushion Diamond Serpentine Ring in PlatinumOld Mine Cushion Diamond Serpentine Ring in Platinum. This modern Erstwhile serpentine antique style engagement ring is as unique as it is stunning. The center stone is a GIA certified old mine cushion cut, which allows the ring to sit low to the finger. The bezel set center stone has no prongs and the under carriage is encrusted with single cut diamonds. On one side of the center diamond, the shoulder of the ring features a mix of old European cut