Small worry stone made from Indian Nuummite (lower grade), also called Coppernite, which is a black gabbro with inclusions that are translucent and reflective/flashy in primarily gold or blue. 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.