Mark:
I am able to run AC12 on OSX10.9.5, but it can be hit and miss. I have kept a hard drive with OSX10.6.8 to run older versions, there is a discussion here:
Archicad 18 on 10.6.8?.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David