Looking for clay core recipes

I'm just processing ALLOT of clay that I dug up. I've got bentonite from cheap cat litter, a fire clay that gave me 12.5% shrink upon drying, I have water glass, perlite, and vermiculite and ABF (already been fired) clay aka grog aka crushed firebrick. I'm planning to mix these things together, well maybe not, yeah definitely, maybe not the vermiculite. I'm interested in anyone's recipe who made a good well insulated core that lasted, or recipes that you tried and don't suggest are just as important. Exact number aren't required. 3 buckets of this and 2 buckets of that works for me.
Also, for those of you who dug your own clay. Did you remove the sand or just the larger impurities? I know people add sand to make cob that goes in the RMH bench and outside, but not for the core and riser correct? or you kept the sand? or did you even add more sand? or add anything else.

Hi Anomika;
 I used  local clay and local sand.  As it was high summer, my clay was dry.   I used a tarp and dumped one 5 gal bucket or so of clay down.  Used a long handle sledge to pulverize it into powder. Any larger rocks are separated then.  3 buckets of sand are poured into tarp and I dry mixed them .  Add water  in smaller amounts as it goes from too dry to way too runny in moments.
That was my cob mix for the mass.   For the core, I used a fireclay and perlite mix as recommended by the masters. No sand.  I think it was 1 part clay to 4 parts perlite, but not sure ,it has been 5 years since I cast a core.
Vermiculite is hazardous , perlite is Not.  Water glass is best used as a  paint on after your core is cast and fired .

Do you have the builders guide to use as a reference?

I will tell you that my cast core, was by far the hottest burning one to date for me. I will also say that I replaced it after one burning season with a firebrick core. My cast RMH with mutable people feeding it  ,could not take the abrasion in the feed tube.  I was constantly patching it.  This is how I know waterglass works best as a paint on.

My next RMH is being started now and it is being built using ceramic fiber boards and blanket. Cost will be significantly more than my humble first cast core.

I'm excited to see if the C.F. products reach the temperatures that my cast core did.

Interesting Tomas. So your riser was fine made out of clay slip and perlite, but the feedtube was breaking? Hmm.. i did here that clay/perlite can withstand heat well, but not physical force as much. Interesting none the less.
Vermiculte is toxic when it burns or you mean it might contain traces of asbestos? Cause I use it in my potting soil all the time. I kinda x-nayed it as candidate for core material anyhow. but would still like to know what you meant.

I an not working from any plans or guides. i know myself well enough to know I'd get to step 3 and start doing my own thing thus wasting my money on a very good guide. I'm just that way. Can't or won't follow simple instructions..lol. I thought about Erin and Erica's guide, but it has been proven so many times over, that I already know it works and how it works.

I want something that I can move, and that doesn't cost much at all. I saw a nice core of just perlite and waterglass with NO CLAY and I thought, i'm going to see what other people have tried and do some experiments myself.

I'm curious why you say waterglass is best as a coating and not as an ingredient in the mix?

I'm out working the clay again today and I'm afraid some sand is going to be in my core mix, because i can't seem to get it all out. lol. So, will see how that goes. otherwise right now i'm thinking.

60% perlite
10% waterglass
10% fireclay w/residual sand
5% bonite
15% grog.

But I changed my mind 3 times as I wrote that.