gpart show
geom disk list -a
geom eli list -a (same as geli list)
geom mirror list -a
geli status
http://www.freebsd.org/doc/en/books/handbook/disks-encrypting.html
To destroy a geli provider used in a zpool, we do
zpool offline zroot ada1p4.eli
geli detach ada1p4.eli
Then, from encrypted to unencrypted
zpool replace zroot ada1p4.eli ada1p4