Fully adjustable. Handcrafted from solid sterling silver with Night Sky Inlay. Direct from the Navajo reservation, the Inlay is made with Jet (black fossilized wood), sterling silver for the round stars, cultured opal is used for the moon, comets and shooting stars. Coral is used for the red moon. Placement of all designs will vary as each ring is inlayed by hand. NIGHT SKY JEWELRY COLLECTION: Inspired by the clear dark night skies of the Navajo Nation. The Black you see is called "JET "and is a fossilized wood, which has been compressed over millions of years. Multiple pieces of stone make up the mosaic image. The stars are made from pieces of silver and the larger star and moon along with the shooting star are made from Cultured Opal. Sterling silver (stars and setting): Is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. Cultured opals (white colored elements), often referred to as opalite, are created in laboratories. Pure opals that occur in nature take many years to develop. Mines of natural opals are found across the globe. In the Southwest United States, there are naturally occurring opal fields that are mined. Jet (black elements) is a product of high-pressure decomposition of wood from millions of years ago, commonly the wood of trees. Jet is found in two forms, hard and soft. Hard jet is the result of carbon compression and salt water; soft jet is the result of carbon compression and fresh water. Native American Navajo and Pueblo tribes of New Mexico were using regionally mined jet for jewelry and the ornamentation of weapons when early Spanish explorers reached the area in the 1500’s.Today these jet deposits are known as Acoma jet, for the Acoma Pueblo.