They are absolutely different! "Mineral" refers to the actual susbstance. "Mineral deposits" refers to a collection of that substance. An example of where you would use "mineral" but "mineral deposits" would be incorrect would be: What kind of minerals are those crystals made of? Another way to think about how they are different is to think about how you would not use "milk" and "glass of milk" in the same way.

Mineral is a natural solid chemical substance. Mineral Deposits are when they build up and stay in a place.