Sterling silver and genuine onyx 

fits size 6.5 inch wrist to 7 inch  best 

chunky 10 mm round beads 

 Onyx primarily refers to the parallel banded variety of the silicate mineral chalcedony. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from white to almost every color. The pure black form is the most famous, especially for beads.
Onyx focuses and directs your energy toward your goals, helping you stay the course. It can help you rebuild your vitality after a prolonged illness or period of depletion, and is useful for work that requires disciplined focus and perseverance.