Shower surround material identification.

RE: a 2008 Komfort TT. I have a small crack that developed in the shower surround between the soap dish and the screw hole that fixes the hose guide to the wall. I've researched possible fixes but need to determine the material to be able to select the correct method. How do I determine if it is fibreglass or plastic?
Thanks in advance and also interested in your experience with a similar problem.