A common logic fallacy, although rarely named. It assumes that because one thing is made out of another thing, it shares the same properties. It goes like this:

If A is X
AND
B is made up out of A's
THEN
B is also X

While this sounds logical, it isn't necessarily true; hence, citing this as 'proof' of something is a fallacy. Observe:

Humans are made out of cells, cells are alive, therefore humans are alive. (true)

Snowflakes are 6 sided, snowballs are made of snowflakes, so snowballs are 6 sided. (false)

I can lift one rock, the mountain is made of rocks, so I can lift the mountain. (Probably false)

And so on. Much like The Fallacy of Division.