Sterling Silver Ring Square Red Center Stone Marcasite Border Size 8.5

Sterling silver ring with a square center stone bordered by marcasite. The ring measures about an 8.5 and is marked 925. The center stone is not cool to the touch so it isn't a gem stone. I have no idea what it is but have seen similar looking rings listed as coral. It is a bright red. The setting is large and a little chunky. Its in great pre-owned condition