User blog comment:Xerav/My Random AD-Caster Item Idea etc/@comment-4012115-20121106215035/@comment-4881935-20121107140033

^ Huge misconception. Spell vamp apply to most abilities and summoner's spell (does not include on hit effects from items and some abilities), regardless if it's physical, magical, or even true damage.

Read the list in Spell Vamp to know more.