Apple not such a great example 

Just as English has a sense of "information" that is countable (See information.), spoiling many a teaching example, "apple" can be used uncountably. It is really not very different from "a grain" vs "grain", except in the relative frequency of the mass senses vs the uncountable senses. Most natural languages confound countable and uncountable in a few ways. For clarity English requires explicit constructions or quantizing or massifying determiners to make explicit what semantic aspect of a word is intended. "A single grain", "a type of grain", "much grain", "a container of grain". It is not hard to imagine a person seeing freight cars full of apples saying: "That's a lot of apple". There may be no English noun that is not both countable and uncountable in some uses.