mat icon which set code example

Example: mat-icon showing text

It will always try to load the local version of "Material Icons" font 
first, before the web font. Therefore, if OP has an outdated or 
customized version of "Material Icons", the desired effect won't be 
shown.

To fix this, delete the local "Material Icons" font, or replace it 
with the latest version if you still want a local copy.