Obsidian now takes less time to mine. It has a more glassy feel to it. You still need a diamond pick to obtain it, or it will just vanish. Download: http://adf.ly/2GPsi
1) Open up %appdata%, if you don't know how to do this, start>run, then type in %appdata%
2) Browse to .minecraft/bin
3) Open up minecraft.jar with WinRAR or 7zip.
4) Drag and drop the downloaded class file into minecraft.jar
5) Delete the META-INF folder in the jar.
6) Run Minecraft, enjoy!