It's great stuff. Here's some comments I made a couple of years ago on another forum:

"It's been marketed as 'Stalite' in the construction trade for many years. We started using it as a soil amendment in post construction sites to preserve and enhance tree roots AGES ago. It has been used as a constituent of what is called 'constructed soils' for urban tree plantings, with great results. It is hugely successful for in-situ plantings, where clayey or compacted soil situations diminish healthful porosity. Its most beneficial application, perhaps, is in areas that may see high traffic (foot or otherwise). Stalite-PermaTill makes it possible to have healthy grass on a baseball field, and healthy trees along an urban streetscape.

It's ALL about oxygen!"

It is not any better than just plain old organic matter. It is sold primarily as a substitute for organic matter but isn't.

Compost disappears. Which one is cheaper in the long run? Compost of expanded shale?

Expanded shale by far. Apparently according to rhizo, it lasts forever and still have positive effect all these years.

Again, it depends on the factors. Don't assume you know it all, Kim.

You say compost disappears, I don't agree. The nutrients get used up, however compost does not disappear.

I am going to be very direct here, Lou. There have been two posts on other threads directed towards rude posts you have made. Either you did not understand the posts were directed towards you, or you are chosing to ignore the protests which have been made regarding rude posts. Rhizo didn't make his case any better than Kim did. Neither of them presented concrete facts, so why are you backing up what Rhizo posted whilst putting down Kimmsr?

If the rest of us remain quiet whilst you bully people, then we are just as guilty as you are by virtue of complicity. Please stop with the putdowns. Disagreeing with somebody doesn't have to be a putdown. I would appreciate your consideration.

Lorna

Yes, compost does dissappear. It is digested by the soil bacteria and the nutrients contained in that compost are utilized by the plants to grow. Yes organic matter must be replaced, annually, because the Soil food Web digests it to feed the plants that are growing there, but this organic matter is, for most of us, readily available and very often free.
This slate may well seperate the clay particles and may well improve drainage in clay soils but what nutrients does slate add to the soil? Does this slate feed the Soil Food Web at all? Is this slate available at very low cost or for free?
Adding this slate is similar to adding sand to clay soil, it really does little to actually improve that clay soil as organic matter does, and it does nothing for sandy soils like organic matter will.

There are some grass areas at a local shopping center where they used this kind of material years ago (1980's). It looked incredibly wierd when they were preparing the soil, but the results speak for themselves. The grass looks fantastic, and drainage, often a big issue for such areas is great. The other plants put in this area are also particularly healthy. This kind of soil addition is used in Europe, at least in Germany, for its environmental benefits. They even build parking lots with open pavers and porus soil underneath so that rain soaks into the parking lot, and does not run off. My experience is that this system works well; even in quite wet conditions, the lots are drivable. In addition, trees growing in the lot look fantastic. Even adding a lot of organic material in the beds will lead decay over time, leading to contour changes, and other effects. For areas where you cannot continue to add the material, or where you want something more permanent, this is good. I have played with a similar material for some small plantings. It does provide a very well aerated medium which plants like basil and peppers just thrive in. I'd suggest giving it a try if you are interested. By the way, you may be able to find it fairly cheap as a bulk loaded material at a local construction agregate facility.
Renais

Okay, so the summary is expanded slate adds no nutrients to the soil, but adds plenty of drainage. And reduces weight. Is it, then, an advantage for container gardening? Especially succulents? I'll cross-post onto cacti.

Love the stuff! If you have clay soils, you can mix in compost and permatill to help loosen in up. The organic matter decomposes, and the permatill remains to promote drainage and to absorb moisture and release it slowly. It also is sold as Vole Bloc. Plant it around your bulbs and its sharp points deter voles.

You also can use it as a planting medium for cuttings and for roof gardens. We used to buy it by the truckload in North Carolina, and I keep hoping it will become readily available here in Ohio.