Req for info: binary key format

[Robert J. Hansen]

Howdy, y'all.  In the process of trying to scratch an itch I
have--namely, no good GNOME visualizations for keyrings--I've run into a
bit of a wall: I can't find a definition for GPG's keyring format.  

The other GNOME visualizations all rely on calling GPG from the command
line, trapping the output, and creating a visualization based off that. 
For a lot of reasons, that doesn't appeal to me--I'd rather just read
the keyring file directly.

Can someone point me to a specification for the keyring file, or point
me to the specific part in the 1.0.6 codebase where I can find it
defined?

Thanks.  :)