This Scottish blood stone, brass & cairngorn brooch is 1 3/4" in diameter. The brass fillagree base is very similar to Miriam Haskell backs. There are for round blood stone disks measuring 3/8" in diameter and 4 diamond shaped.
Blood stone is Plasma with red sports of iron oxide. Plasma is dark green, opaque chalcedonly quartz with the color coming from the chlorite.