Usually the fine is horticulture grade and chunky is used for poured insulation inside cinderblock. Try your building supply store. Billie

Paws ask about Zonolite.
If they have that they can provide you with all the chunky vermiculite you will ever need.:)

Thanks. Will check out this weekend. Love the look of vermiculite now want to try chunky stuff.
Paws

Paws, Believe Zonolite was removed from the market because that was one of the name brands that had asbestos in it. Not positive but when I did a search to recheck it was only bringing up asbestos warnings for that name brand. This all happened years ago so don't be panicing about new vermiculite. BUT if you're holding on to old Zonolite the EPA needs you to dispose of this properly. Billie

I get the big vermiculite at Menards around $9:00 a bag and I have used it in making hypertufa

"Paws, I Believe Zonolite was removed from the market"

That should be news to Rick on the sunshine coast (his cryogenic perlite is the Zonolite brand).
I ordered 4 different Zonolite products last week including vermiculite.

Here is a link that might be useful: Zonolite is alive and well.

I wonder if anyone has used portland and just vermiculite in place of sand. I'm thinking about trying it but don't know what ratio to use.

Yes, I have used only portland, peat and vermiculite and have pieces that were made many years ago and they fare well through the winters here and are much lighter in weight than those made with sand. In fact the things that I've made this year are the only things I've made with sand.
spiderwoman

Fleur - I've tried mixes of Portland 25% and Vermiculite 75% and some with even less Portland and more Vermiculite. The results looked O.K., but the castings were very lightweight. I haven't repeated the recipe because I'm interested mainly in making garden lanterns, and a lantern as light as these were is too easily knocked over - even by squirrels and birds. As for their strength - I think that half the secret is using as little water as possible in your mix.

Herb

my mix is equal parts portland, peat, and vermiculite, I can get it in fine (at cement place) or medium or course grade at garden center. the look is slightly different but I do notice a big difference in the feel as I mix it. The finished product is the same as far as wear and tear. I have some that have wintered 4 or 5 years here in NY and they are great looking.

Herb - I wanted something lightweight to put a topcoat on the backside of a large ornamental rhubarb which had several tips broken off and reattached. The backside looks like a patchwork quilt. I want to smooth out the backside, let it rest for a few days with misting and then plunk it into a kiddie pool for a few weeks. The leaf was originally cast almost two weeks ago. I hope the cement/vermiculite mix bonds to the back side of the leaf. I've got some quickrete bonding stuff but I'm not sure how to use it in this instance. Nor do I know if it's waterproof.

Since I'm so new at this, all my efforts are experimental so far. I learn by doing...and by my mistakes.