Superb antique French 18K yellow gold hat pin, stick pin brooch. The top in the form of an arrow fletching, the feathers decorated with diamonds. Featuring 42 rose cut diamonds set on silver over 18K gold mount. Centered by a cylinder cut chalcedony stone in a warm amber color, (perhaps agate). Having a ported back, allowing light to pass freely through the diamonds resulting in greater brilliance and shine as the pin is worn. Hallmarked to the back of the mount as well as on the pin, with the French control mark indicating 18k gold content, in the form of an eagle's head, in use in France from 1838. Also bearing a goldsmith's mark. In overall good antique condition. Measures 6" length x 3/4" widest.