I'm making my new texturepack and i descover this new item (Its not emerald) You can download my texturepack here: (beta) AdFly: http://adf.ly/9UKAr Direct(MediaFire): http://www.mediafire.com/download.php?mdx8pl0vizcdwyc (Pleae if you want to support me download it from the adfly link)
First they planned to add Rubies but decided to do Emeralds instead. The "Ruby" texture is still there, just unused.
They remove the chest textures from the terrain.png so they update the items.png (but i am not so sure )