Ohh dear, you are not supposed to do that on a jailbroken iPhone. That is why it is taking so long.
To do a fresh restore follow these steps
1. Download the 6.1.2 firmware (Google -"Where to download iPhone Firmware iClarified")
2. Once you finished downloading the ipsw file (download using Firefox or if you download using IE, rename the file to ipsw extension instead of the .zip extension)
3. Connect your iPhone to your computer and run iTunes
4. Click on your iPhone on the left sidebar in iTunes
5. Press the Shift key on your keyboard and AT THE SAME TIME press the "Restore iPhone" button in iTunes
6. A window will open asking you to choose the ipsw file you have downloaded
It will take 10 minutes for iTunes to wipe your iPhone and install the new firmware.