Rainbow Moonstone Sterling Silver Cuff Adjustable.  Rainbow moonstone is also known as white labrodorite a closely related feldspar mineral with sheen in a variety of iridescent color.  Moonstone is often called the visionary's stone as it helps us see things more clearly.
 
Approximate Dimensions -
Bracelet size - 6 3/4" adjustable
Rainbow Moonstone Size - 1 1/2" by 1"