.EMERALD File Extension
What is an EMERALD file?
Theme designed for the Compiz Window Manager that can be applied using the Emerald Window Decorator; saved in a package format that includes several button images, a screenshot, and a "theme.ini" file; can be installed and edited using the Emerald Theme Manager.
The Emerald Window Decorator is included with Compiz Fusion, a composite window manager for Unix systems. In order for the Emerald Window Decorator to function, the "Decoration" plugin must be installed.