A semi-precious gemstone with a smooth, polished surface that exhibits a play-of-color effect, showcasing vibrant hues of blue, green, and red when light hits it at different angles. The opal is typically oval or round in shape, with a slightly irregular surface that enhances its natural, organic appearance. Its base color can range from milky white to dark black, with the play-of-color appearing as fiery flashes or subtle shimmering patterns across its surface.