This pretty triangular shaped pin has a raised rose in the center mounted on an engraved triangle of gold plate.  Below is an ornate boarder of S-shaped wire work and small marcasite stones that are bead set with tiny burrs of metal.  This pin would be considered a bar pin such as was worn in the later part of the 19th Century circa 1890.  Measures 2 1/4" wide by 7/8" tall.

View of pin stem: