I'm trying to access the file of a pre-installed font on OSX. Where is the location of core, pre-installed fonts on OSX? The Library folder only contains fonts you've installed.
Apple provides a list of directories here: http://support.apple.com/kb/HT2435
Each user has complete control over the fonts installed in their Home. These fonts are available to that user when he or she is logged in to the computer. Fonts installed here are not available to all users of the computer.
Any local user of the computer can use fonts installed in this folder. Mac OS X does not require these additional fonts for system operation. An admin user can modify the contents of this folder. This is the recommended location for fonts that are shared among applications.
The Network folder is for fonts shared among all users of a local area network. This feature is normally used on network file servers, under the control of a network administrator.
Mac OS X requires fonts in this folder for system use and displays. They should not be manually altered or removed.
This folder contains fonts used by the Classic environment (Mac OS X v10.4 or earlier only). If more than one Mac OS 9.1 System Folder is present, only fonts in the System Folder selected in the Classic pane of System Preferences are used. Classic applications can access only these fonts, not those stored elsewhere. Conversely, Mac OS X applications can use these fonts, even when the Classic environment is not active.
The default install of Mac OS X includes fonts in both of the following folders:
While I believe the following Fonts folder exists, there are no fonts installed in it by default:
Alternatively, if you know the name of the font, you can select it in Font Book.app and choose Preview > Show Font Info. The location is listed like in the image below.
You can also right-click (Control-click) on the font in the "Font" column and choose "Reveal in Finder"