Will transmogrifying an item delete it?

Does transmogrifying an item destroy the item?

I raise the question on either end.

For example, I decide to transmogrify my assassin's chest piece into, oh, let's say the chest from the druid t6 set.

Is my assassin's chest piece destroyed in this process?

Is my t6 chest piece destroyed?

Do the two items turn into one new item, or will only the assassin's chest piece morph, for example, into a copy of the t6 piece, leaving the t6 piece untouched?

For that matter, will the assassin's chest piece be untouched, and a third, totally new item be created, with the appearance of t6 and the stats from the assassin's chest piece?

For that matter, will I be able to transmogrify an item multiple times?

Let's say, for example, that my assassin's chest piece is transmogrified into the t6 chest piece.

Now, I get a new drop from firelands, and the stats are an upgrade, but I want to keep the t6 look.

Can I transmogrify the transmogrified assassin's chest piece with the new drop, and get the look of t6?