Small worry stone made from Scolecite, a mineral with fibrous needles that can appear similar to selenite. Worry stones are an oval shape with a slightly concave indentation for your thumb, and are polished smooth. 

Approximately:
1.25" x 1.5"
3 cm x 4 cm

Picture is representative of the product you will receive, but may not be the exact stone. Each stone will vary slightly in color, pattern, and shape.

Secondary picture shows other worry stones available here.