Question About Professor skill....

[Palmolive]

Does Double Casting affects the Earth Spike skill?...
Because Earth Spike's description is an earth element bolt, which means Double Casting or
(Double Bolt in iRO name) can make the all bolt skill double release...

is it true?...

[xyuki]

Only Fire/Lightning/Cold Bolt are affected by this skill.
Earth spike, sadly, isn't.

You can read it up on iRO wiki.