Yellow Calcite crystal thumb / worry stones.  The colouring of these stones is pale yellow and white with natural banding.  The backs are flat and the front sides have indentations which should be used to rub your thumb over to distract your mind and reduce worry and stress.  Some of the stones have slightly rough areas.  

This stone Is useful if you're a mature student or want to retrain.

See more thumb / worry stones here

Country of origin: Mexico

Size: 5 x 3.5 x 1 cm approx measured at the largest points
Weight: 31 - 33 grams approx