Milling The St Cloud Granite

[Kaolinwasher]

I have been working with the St Cloud Granite, and milled some up today , you can see the rock on the picture next to the milled granite , it has layers after settling ,  and some of it looks like iron ocher,   even after sitting one day  i get this fine material that just will not settle down so i pour that into a jar and add some vinegar and it settles out , but it is so fine i have to put it in a bisq fired bowl or it will go thru the cloth i use  and that way recover it 

[Mark C.]

Is this going to be milkshake? looks good on ice

[Kaolinwasher]

it kinda looks like one , i have to agree,

[terrim8]

Did you build your own ball mill? It looks kind of weathered so if there is any pyrite or  other metal sulphides will disintegrate easily into solution. Can you get some fresher granite? Might have to bash away at it for awhile but it'll be better for the quartz and feldspar content. 

 

One article about it is quoted below- no mention of sulphides but it did go on to further state that it has magnetite in varying amounts. Fe3O4 i.e. iron ore. I don't believe that there wouldn't be some pyrite in it though.

 

 "St. Cloud Granite. This granite has a “uranium-lead age date of approximately 1.77 billion years†(Boerboom & Holm 2000). The St. Cloud Granite is a “coarse-grained, dusky red-colored hornblende granite, with a distinctive mottled pink and black color†(Boerboom & Holm, 2000). The major minerals that make up the composition of the St. Cloud granite are potassium feldspar (microcline), quartz, hornblende and biotite." 

 

Those last two silicates contain iron too.

[Kaolinwasher]

Yes i did build my own ball mill .and tumble with soux quartzite, and or agate and quartz, for about 8 hr  gets it down to 200+ mesh i like this granite because it has iron in it . 2 to 3% and it is pottashdominant ,  and will go well with the anoka sand.  also i found out about a Loess deposits in preston MN that is really nice and the Decora shale  i think i do more testing of materials than making pots.  coming up in my next test cone 8 reduction firing i will have a celadon made from this granite or using some of it . also i have worked with the wasau a granite in wisconsin  and it is top notch material  very low Ti along with the Redgranite, and the Berlin ryolite from berlin Wisconsin . very good stones for glaze.  have yet to test the berlin and red granite tho but they  have good makeup .  also the Reformatory granodiorite interests me  but to say the least lots of good granite all over the U,S 

[terrim8]

Sounds like fun. I have yet to build my own ball mill but I want to. You should try some of the more mafic rocks in your area then report back here- esp. if you get a hold of some anorthosite and gabbro- I'd like to see how that works out. I have access to some quartz monzonite and aplite plus some hydrothermal clays but they are contaminated with sulphides and I don't know how to clean it up- do you know? Perhaps the method is in your name? 

Did you read about the Chinese loess that produces a temoku glaze? So much fun to get our glazes this way- we should compare notes. 

[Kaolinwasher]

I have heard of loees in china , but not that it made a nice temoku glaze  that sounds intresting . as to how to get the sulper out of clay i do not know . other than oxidizing it and washing it out .  we know to get the sulpher out of our clay it must be burned in oxidation. but reduction will not work  . on the quartze monzite try bisq firing it and then get it wet and smash it to sand with a hammer  then ball mill it  one thing i have found is the mafic rocks are harder to crush . one i was hitting with a sleg hammer as hard as i could and it just would not break i had to fire the stone up to 1800 f and it finally started to crack and melt  but i tossed it  they tend to make matt greens , but i am open to the idea . of using them , 

[Guest JBaymore]

I get my granite from a local granite quarry a few miles from my house (NH ->"The Granite State").  From cutting, they produce a lot of what they call "dust".... which is anything from fines up to about 3/8" chunks.  For glazes I ball mill it for 6 hours (used to be in a home-made mill.... now a large double jar Shimpo ball mill). I use commercial porcelain balls.

 

Because they do architectural work with the granite... they have to have technical data on representative samples for the architects and engineers.......... so I can get analysis of the rock composition that is fairly close for glaze calc use.

 

It is a nice base for glazes.  I also use a local clay deposit.  And wood ash from my winter heating wood stove.

 

best,

 

...................john

[Marcia Selsor]

John,

What is in your granite? Is it basically a feldspar? Just curious.

 

Marcia

[terrim8]

I'll have to check out that Shimpo ball mill. Easier than building one myself- as usual all I need is mucho denaros.  Good to hear that the New Hampshire granite works good as a base glaze, so the quartz monzonite will likely act the same way - 2/3  orthosclase & plagioclase feldspars, 1/3 quartz. Sort of a glaze reddi-mix except for the need to mill. How noisy is the Shimpo?

[Kaolinwasher]

John , how do the porcelain grinding balls wear,?  are they high alumina ? was thinking of getting some ,  sounds like you have some very nice granite to use . what i do is take a chip off a stone and put it in with a cone 8 firing  and just see how it melts  and if i like it  i use it . i tried some from mill bank S,D and it made a jade like green of a nice gem quality, Terrim8 that monzonite would probably work great . each stone has its own look. and texture.

[Guest JBaymore]

I'll have to check out that Shimpo ball mill. Easier than building one myself- as usual all I need is mucho denaros.  Good to hear that the New Hampshire granite works good as a base glaze, so the quartz monzonite will likely act the same way - 2/3  orthosclase & plagioclase feldspars, 1/3 quartz. Sort of a glaze reddi-mix except for the need to mill. How noisy is the Shimpo?

 

 

John , how do the porcelain grinding balls wear,?  are they high alumina ?

 

The Shimpo dual jar mill is very nicely built.  Rugged.  But yes.... a bit expensive.  (However I patched up my home built mill way too often.  Sometimes spending money is cheap.)  I have a pair of the largest porcelain jars they make as well as some smaller ones.   Depends on what I am milling.   Unfortunately... the mill itself is not noisy, but the charge with the balls is.  The erosion of the balls is not all that fast and seems to not affect the grind negatively -with excess contaminant of SiO₂ / Al₂O₃. 

 

best,

 

...................john

[Marcia Selsor]

So John,

do you have a breakdown on the granite molecular structure. I imagine it is like the old "theoretical" spars in the worksheets.

Marcia

[Guest JBaymore]

So John,

do you have a breakdown on the granite molecular structure. I imagine it is like the old "theoretical" spars in the worksheets.

Marcia

 

I have the molecular oxide percentage analysis (pretty detailed .... not like theoretical spars) and some structural strength data (for the blocks... not the dust  ).

 

best,

 

...................john

[Marcia Selsor]

Thanks. I was wondering how you incorporate it into you glazes or do you use chunkier pieces in your lay.

 

Marcia

[janicehill225]

If any of you have some successful recipes that you have used with granite, I'd love to know them. I'm working with a group of wood firers who are trying to reproduce local clays and glazes used by Cyrus Cobburn, a Georgia folk potter who was in Junction City, GA from 1830-1840. I have access to local granite dust, a gneiss- hornblende potassium feldspar. I also have access to Georgia kaolin, 200 mesh silica sand, lime stone, Lizella clay and a blue creek clay that is a ball clay.  Here is a picture of a granite-based celadon from our last firing. The recipe is 7% oakwood ash, 25% Georgia kaolin, 29% silica, 17% whiting and 22% granite dust.

 

[Kaolinwasher]

hay your picture did not show - I gota see that celadon .   sounds cool

[Guest JBaymore]

If any of you have some successful recipes that you have used with granite, I'd love to know them.

 

Run a triaxial with your granite, any local clay, any local wood ash.  That likely will keep you in ideas for a long while.

 

One of my glazes is 33.33% granite, 33.33% local red clay from up the river from my house, and 33.33% mixed hardwood ash from my woodstove.  Another is 25% granite, 25% (milled) sand from the riverbank on my property, 25% mixed hardwood ash, and 25% of local clay.

 

This is the 1/3, 1/3, 1/3 glaze: 

 

With local materials... it is all about testing.

 

best,

 

...............john

[Kaolinwasher]

intresting, glaze, looks like moss growing on a stone ,  nice looking clay body to 

[janicehill225]

 

 

 

If any of you have some successful recipes that you have used with granite, I'd love to know them.

 

Run a triaxial with your granite, any local clay, any local wood ash.  That likely will keep you in ideas for a long while.

 

One of my glazes is 33.33% granite, 33.33% local red clay from up the river from my house, and 33.33% mixed hardwood ash from my woodstove.  Another is 25% granite, 25% (milled) sand from the riverbank on my property, 25% mixed hardwood ash, and 25% of local clay.

 

This is the 1/3, 1/3, 1/3 glaze: 

 

With local materials... it is all about testing.

 

best,

 

...............john

 

So many tests I've done.  I was hoping for a leg up.

[janicehill225]

hay your picture did not show - I gota see that celadon .   sounds cool

Here it is.

[Kaolinwasher]

right out of the han dynasty.  thanks , looks nice