Some is a determiner that can be used with mass nouns and plural countable nouns.
See the following examples. The use of some in the first sentence alters the meaning.
He had some ice cream on his face. -mass noun
He had an ice cream. - countable noun
some money - mass/uncountable noun
some of the money - a part of the money
Some of the book [ a part of the book] is dirty.
Some of the books are dirty.