Grit

[Alan B]

I've been looking back through some of the old logs about the grit Ian uses. Log 25/07 in particular.  I have always bought grit by the bag from the local Garden Centre but now have a source available for 0-4mm crushed slate.  Anyone out there know anything about trace minerals etc that might be in this material?  Tests I have done with it certainly show that mixed with a compost it will give good drainage.

[David Nicholson]

Just in case this might be useful Alan.

http://www.slate-stone.com/chemical-properties.html

[Alan B]

Thanks for that David.  Some food for thought there. 

[Maggi Young]

We've never tried crushed slate of that size for the purpose of substituting for grit  but , though you say the drainage rates seem good, I would worry about later compaction because of the flatter nature of slate flakes  Also, given the sharp edges you get with slate flakes, might not even these tiny ones be like planting things in glass slivers and slice the roots to bits?? 

[DaveM]

Alan, I haven't tried using slate either, and probably wouldn't. Reading the web site mentioned by David, you will see that the composition of slate may be variable depending on source:
I quote (my emphasis):
"Slate ...  is ....a multi-mineral rock made of an aggregate of minerals and colloidal substances. Essentially mineral composition includes members of Mica group commonly sericite & muscovite, Clay group commonly paragonite, chlorite & kaolinite. The accessory minerals are oxides, calcites & minor amounts of quartz and feldspar along with subordinate amounts of ferro-magnesium minerals. Free silica is normally poor."

Many slates (particularly the grey Welsh and western Highlands varieties) contain very substantial amounts of the white micas listed above. These minerals (and quartz) are VERY resistent to chemical weathering processes: ie they are almost inert. That's why much of the highlands (that which is underlain by mica schist) has very poor soils. These slates are unlikely in my opinion to provide much in the way of nutrients. The exception might be the green Lake District slate which has a volcanic origin and is rich in chlorite, a magnesium aluminium silicate, which does break down by chemical weathering processes.

As for the aeration/drainage properties of slate. I'm not sure that it is the equal of the more equant graded grains of say granite or dolerite, or even quartzite.

Hope this helps

[Alan B]

Thanks for your comments everyone.  Tends to look as though it is probably a non starter.  I had hoped that as I could have as much as I needed for free it would could save me some cash but I think I will be sticking to the tried and tested!!

[Ezeiza]

Hi:

     But since it is obvious that the material is inert and it is for free, the problem you have is the dust fraction (was it 0-5 mm. right?) that will clog the mix air pores.
 
     If there is no problem to sieve it (say leave it in 3-5) then you have a great amendment before you.

      Maggi, the sharp edges of the particles poise no problem as roots will wander at will about them. Our granite sand is similar and plants thrive in it .


Regards

[Rafa]

JJAJAJA ¡¡mira quién se registró!! ya era hora de que participaras un poco y salieras de tu cueva. Al principuio ayer me sospeché que habías estado siguiendo mis topics en el foro, indagando un poco sobre mis cyber-actividades pero no creí que llegarías a tanto. ¡¡Cambiate el nick que se te ve el plumero!! aqui hay viejos amigos tuyos muy amantes, demasiado diría yo  de los hipp.

Abrazo

[David Nicholson]

JJAJAJA ¡¡mira quién se registró!! ya era hora de que participaras un poco y salieras de tu cueva. Al principuio ayer me sospeché que habías estado siguiendo mis topics en el foro, indagando un poco sobre mis cyber-actividades pero no creí que llegarías a tanto. ¡¡Cambiate el nick que se te ve el plumero!! aqui hay viejos amigos tuyos muy amantes, demasiado diría yo  de los hipp.

Abrazo

Rafa, my Spanish is not as good as your English (well languages are not an English strongpoint, are they!!) so could you add a translation please?

[ChrisB]

Dave - I put it on the translation site and this is what it gave me:

JJAJAJA look who saw! It was time for a little involved and out at your cave. At yesterday principuio I suspected you had been following my topics at the forum, a little investigating on my cyber-activities, but I did not believe that to reach both. Cambiate the nickname that you see the plumero! Here are old friends of yours very loving, I would say too much of hipp.

Clearly not one that does a perfect job, but you get the drift....

[Rafa]

I think this new user "Ezeiza" is an old (very OLD!!) friend from Argentina who are an absolute bulbs expert!!

[Ezeiza]

UGGGHHH!!

                 the translator sucks!


This is what he wrote (tongue in cheek)




JJAJAJA Look who logged in!! It was about time you join in for a while and get off your cave. At first I suspected you were following my topics in this forum and inquiring about my cyber-activities but never thought you would get this far. Change your nickname, your tail feathers show out!! There are old friends of yours here, lovers, too much I would add, of hipp.

Hug

[David Nicholson]

Ah! I see

[Rafa]

CAPULLO!

David, thank you for tell me that my english is good but as you can see is also like a babelfish translator!

[ChrisB]

I know, but its better than nothing at all.  I use them sometimes.  You should see what they are doing to botanical descriptions from your armeria pages you sent me Rafa.  Sometimes I laugh out loud at what they translate.  But they are robots after all.....