This is the FreeCAD standard material library. Its intended to gather the most commen Material definitions. 
How to do a description is explained here:
http://www.freecadweb.org/wiki/index.php?title=Material

To make the material description usefull for a lot of application only files with the (CC BY 3.0) license
will be accepted into the FreeCAD source distribution. For more detail about the license see here:
http://creativecommons.org/

Please help! 
Enlargen the base of Materials for FreeCAD will greatly benefit the usability of FreeCAD. So please 
help us to add new Materials, review existing ones or add additional vlaues. A good source for material 
defininitons are text-books or the www.matweb.com database.

2013 Juergen Riegel 