Amazing example of a "Life Size" bulls eye agate - this really is something special. It is about the size of an actual bulls' eye and has a black ring then two white rings and a milky surround to the most amazing crystalline formation in the centre. This would most definitely have been a "specimen" brooch bought for showing and may have been worn or kept in a cabinet for showing.
Size is: 3.5cm (1 1/4") Diameter x 1.2cm (1/2") thick
Framed in sterling silver (tested) and fastens with a secure pin and c clasp