Perlite is great until it inevitably floats to the top when you water your plants! I got the quartzite at a farm supply store. It's called Cherry Stone chicken grit. I'm pretty sure it comes in different sizes. The size I have is slightly smaller than your average aquarium gravel.Where do you get your quarzite? That sounds pretty! I've been looking for something other thank perlite or coarse sand to use, like some kind of rock type thind, but stuff at the hardware store seems too big. I'm using some old aquarium gravel to supplement some of the perlite and succulent soil mix because that is what I had on hand.
If they are not wrinkly, they should be still happy if you haven't watered them. I've read some lithops species may get enough from the air or just need to be sprayed and not a full water, while others do. Sounds like yours are doing well! Splitting is a good sign. They are doing their thing