I looked for the Workspace Icon ( a database cylinder ), but I could not find it. While inspection showed that it was part of the core.min.css. After an hour of searching I looked at the source files in Firebug. There are two versions of this css file, one in the apex_ui folder and one in the app_ui folder.
I have created a page where both collections of icons are listed:
Press the button above to visit the page.
You can toggle the list between the standard icons or all the icons.
The icons can be used in HTML by adding the classes a-Icon and the class of the specific icon (the text behind the icon on the page):
<span class=”a-Icon icon-find”></span>
The Apex Builder icons can be used by referencing the file apex_icons.css. Put this file on your server or in the static files and reference it on the page with the icons.
Have fun using the icons,
Source Article from http://dickdral.blogspot.com/2016/06/hidden-treasure-apex-5-icons.html