granite grit, perlite and turface would do for the entire pot

I thought I read somewhere that lithops needed some organic material in the mix. Is this not the case?

I've actually omitted the sand from the mix. Since the mixture is mostly drainage, I've found that it doesn't really make much difference between using the mix entirely vs. pebbles at the top, as it is pretty airy already.

Hey Tee, are you in T.O.? If so, we're pretty close neighbors.

Your mix sounds pretty good, maybe you could post a picture of it? Lithops absolutely DO need organic material and a decent amount of fines in the mix along with some actual clay dirt, filtered of course. The proportions of these depend on your environment.
In very arid climates, the mix can be 50-60% local loamy clay dirt along with equal proportions perlite, vermiculite and coir. This mix retains water longer but in the desert, it still dries out in 1 day. That same mix would stay wet for a week here on the coast.

The mix I use for Mesembs starts with about 50% sifted potting soil (bark). The other 50% is equal parts volcanic pumice and turface. That's step 1.
I then filter out the big chunks (over 3/16") for a finer grit. To this, I add about 1/10th proportions of horticultural sand, pure coco peat and dirt from my backyard. I think of the fines as lubrication for all that grit, something for the fine roots to navigate through.

I'm still experimenting with my mix but my plants seem relatively happy with the current situation. I'm probably going to start adding vermiculite as well.
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T,

Listen to what Ryan has to say - he's been reveling in Mesemb Madness for some time. About the ability to absorb water, yes, that's true, but (always with the buts) you'd want them to do so only when they're growing - there are periods when it's better to not water, too.

Ryan,

He's part of our Canadian gang - when I saw TO I thought Toronto / Greater Toronto Area (GTA, as I hear on newscasts). I'm telling you, the discovery of a Nunavut Nananthus is just around the corner.

Yes, I'm Toronto.

My mix (at least the latest version) is 1 part each of potting soil, coir, perlite, and 2 parts each of grit and turface. I ended up omitting the sand because it seemed all the fine particles sunk to the bottom of my bag, so it became difficult to re-distribute throughout the mix. Here's a pic:

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It can get pretty dry here in the winter, but summers can be humid, and given my history of drowning cacti, I decided to go for a higher proportion of drainage material and less organic. I really don't know how well this will work, but it does seem to dry quickly. I watered my new lithops yesterday morning and it already looks pretty dry today.

Days are getting shorter here and I'm only getting direct sunlight until about 10am these days (east-facing window), so I may not water again until the spring, unless they look unusually wrinkly.

BTW, I have one that is flowering right now - I'm waiting until it's finished flowering until I repot it into my soil mix. Check it out:

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