I think what you meant to say is The area features a variety of rock types including basalt columns, mixed volcanics and most notably granite.
What John wrote is the meaning we intended, although the way you wrote it is bulkier.
I've got two English majors double checking it now, although I am pretty darn sure it is correct as written. Here's why: First, unless "especially granite" itself is a unique type of rock, there must be a comma between the words "especially" and "granite."
Second, commas usually denote pauses in speech. Read the sentence out loud, pausing briefly at each comma, and you arrive at exactly the meaning John described above.
Third, commas between distinct subjects are mandatory (such as here) the comma between "basalt columns" and "mixed volcanic rock." However, if different subjects are separated by the word "and," that same comma becomes optional. We omitted the optional comma between "columns" and "and" because the comma after the word "and" seemed necessary (and three commas would have been too much).
A lot of thought went into this exact sequence, but that doesn't mean it is necessarily correct or even best. I'll comment again when my experts say more.
As a side note: Adam, you're not allowed to buy a copy unless you pledge that you will actually use the damn thing!
