External Drive recognized but not mounted, Disk Utility no erase option availible

Howdy hallmackenreuter,

If I understand correctly you are wanting to erase your drive and its partitions, but you dont have those options available in the Disk Utility. From your screenshot it looks like you are booted into the OS itself, and what you are seeing is expected when you are logged in. You need to do this when booted to the Recovery Mode. This article will help you do that:

OS X: How to erase and install

Important: Before you erase and reinstall, back up your essential files. If you’re installing on a notebook computer, make sure your power adapter is connected and plugged in.

Use these steps if you need to erase a disk before installing OS X:

1. Before you begin, you need to be connected to the Internet.
2. Choose Apple menu > Restart, and then hold down the Command (⌘) and R keys while the computer restarts.
3. Select “Disk Utility,” and then click Continue.
4. Select your startup disk from the list on the left, and then click the Erase tab.
5. From the Format pop-up menu, select Mac OS Extended (Journaled), type a name for your disk, and then click Erase.
6. After the disk has been erased, choose Disk Utility > Quit Disk Utility.
7. If you’re not connected to the Internet, choose a network from the Wi-Fi menu in the right corner of the menu bar (in the top-right corner of the screen).
8. Select Reinstall Mac OS X, click Continue, and then follow the instructions.

Learn more

OS X includes a built-in Recovery system that you can use to reinstall Mac OS X, repair a disk, restore from a Time Machine backup, and more. To use the recovery system, restart your computer while holding down the Command (⌘) and R keys. If you want, you can also install OS X on an external drive, or create an external recovery disk.

Thank you for using Apple Support Communities.

All the best,

Sterling

Are you booted into your external drive (or your internal)? How did the external become a logical volume group?

Since you are wanting to erase the external, you should be able to do that while booted from the internal - there is usually no need to use recovery to erase an external drive.