I was just there this past week (and have been here many many times). Though I can't definitively answer your question, I believe the beach is mostly sand. I was walking on it in bare feet and it was fine, though there are definitely "seams" of sea shells along the shore a few feet wide that wash up.
I've sat on this beach, walked the beach, sun bathed in the beach and it's never been uncomfy. That being said, when I'm at the hotel, I usually grab a chair in the grass by a palm tree and chill out.
Side note... Still love this hotel. Been coming here for 10 years. Always treated well, usually upgraded, club lounge is great, and I love th location. This hotel, though small, has a lot of action going on, which I like.