Natural solid Australian boulder opal from Queensland area, cut and polished to show it's natural beauty, set in 925 stamped sterling silver setting with bail. 925 stamp is located at the bottom of a setting on a back side. Dimensions: 25x13x3.5 mm. Opal colors: blue and green, with some orange as well present. Play of color depends on lights condition, pictures are made indoors with artificial light and outdoors with natural light. Untreated, just straight from the ground to finished piece of jewelry. 50(+5)cm strap is included, so you can wear it right away. Australian opal is a sedimentary variety which is stable, is not affected by contract with any liquids and can last very long time if is used with care. Opal itself is relatively soft stone, but this setting gives it a good protection.