In order to test the Beta and Gamma radiation with the Radiation Sensor Board for Arduino we can use small pieces of Vaseline Glass. This material contains a very small amount of uranium (0.2%) usually in oxide diuranate form. This material has fluorescent properties when charged with ultraviolet light.
Read more about the Vaseline Glass.
It is sold in a bag with several glass beads for testing purposes (beads can vary from the original image).