How to hard brick an android phone (Galaxy Nexus)? I'm trying to figure out whether or not I managed to brick my android phone, a Galaxy Nexus*.

Using ClockworkMod Recovery, I pretty much erased everything I could find (/data, /cache, /factory, /system, /boot, /sbl, /xloader). If I reboot now, will I still be able to boot into ClockworkMod? Specifically, /recovery is not on said list.

I am trying to find information on how the boot process works, but it is very hard to discover around the web among all the end-user specific noise. As far as I understand it, there is a stage-one bootloader in an actual ROM (emphasis on read-only), but I do not know whether the fastboot-functionality is contained in it.

Hypothetically speaking, if I were (able) to zero every block of the internal SD-card sans the read-only ROM, would that brick the device?

To my knowledge, as long as I can still get into fastboot, the device is not bricked? If all this fails, can I use special hardware to restore it?

*: I should note it is currently powered on and has loaded the ClockworkMod Recovery. I believe I could get it back to working order, but I really want to find the minimum amount of software I can get away with.
As far as I know, your device is not that hard bricked, that you can't boot into the bootloader (fastboot mode). so at every time you should be able to install a custom recovery via fastboot flash recovery recovery.img. if you are in recovery mode with a working recovery, you can do a factory reset (reflash the system, root,... partitions from a protected image) and reboot your device. alternatively you can do a factory reset in fastboot mode.

note: if you erased everything, your recovery will freeze like if you pull off the hard drive from a running Linux. also there are partitions, you are never able to flash, as example the RADIO partition, fastboot or the one, containing the factory reset data. (RADIO partitions contains fine tuned configuration and management of the gprs, lte,... modem)