This appears to be a vintage sterling silver and black onyx ring featuring a bezel-set circular cabochon stone. Unmarked 

• Design Features: The setting includes a twisted rope wirework border around the center stone and detailed foliate or leaf-pattern shoulders along the band. 

• Metal Composition: Pieces in this distinct Arts & Crafts or Southwestern aesthetic are commonly crafted from 925 sterling silver with an antiqued or oxidized finish to highlight the embossed detail

• The current estimated market value for this type of vintage sterling silver black onyx ring typically ranges from $25 to $60 on secondary marketplaces like eBay and Etsy