If A Spellcaster is interrupted while casting a spell that has an expensive material component, is that component lost?
Example: A wizard starts casting Stoneskin and the fighter gets an attack of opportunity. He hits, and the wizard fails his concentration check. The spell is lost, does the wizard lose his granite and diamond dust worth 250g?
I believe the answer is yes, but I am just making sure I am not missing anything. The PRD says "If you fail the check, you lose the spell just as if you had cast it to no effect."
So it is as if the wizard had fully cast the spell, including using the material component, even though he never finished casting the spell.
Full disclosure: I came to this question in my research on using Blood Money with spells that take longer than 1 round to cast. I couldn't find any information for when the material component is used. This is the closest information I could find in the rules about it. If the component is lost from an interrupted spell, it means the component is being used right from the start.