Gold fill on silver (most likely). Bohemian garnets, as these stones/jewelry pieces are known, were made in what's now the Czech Republic around the turn of the 20th century, c. 1900. They were almost always rose cuts set close together like this, with a glowing red color, and were made in non-precious metals like silver/gilt. Moons and stars were popular subjects, and the best pieces are kind of witchy, like this. Moon is 1 1/4" diameter, not including ring at top.