Is grantite dust in potting medium okay to use?

[newstart]

I have found at my local builders yard 'granite dust'. I took a sample and to all accounts it looks ideal for a potting medium as a substitute to grit. Does it tend to be cheaper than grit when bought in bags. I noticed I can get it in bags of 40Kg which should bring the price down a little compared with 25kg grit bags in theory? . It has a mixture of 3mm,5mm,6mm, 9mm, 1cm but is thinner the other way ie it is never 1cm x 1cm as gravel would be. So the biggest particle is 1cm x 6mm but most are smaller as above both ways. It is like slightly bigger grit if you like. The granite looks solid and consistent like grit also. I thought I'd save money as less pieces of granite are needed being 'very slightly' bigger. Does it have an affect on plants or is it okay ?

I live in the midlands if that helps.

Thanks again David.

[ranunculus]

Hi David,
When I was purchasing building materials for a living I tried granite dust in any number of compost mixes and the only real problem was the 'dust' element ... much of the bulk can comprise this dirty dust which can stain terracotta pots and detract from the draining properties of the granite chips.  It seems silly to buy large bags and then spend all day sieving out the dust ... why don't you consider large bags of road chippings - the same granite chippings that you can see piled up in lay-bys all over the country? Many quarries and some builders merchants will sell this very cheaply.

[gote]

It all depends upon your facilities. I would wash out the dust by putting it in a bucket and running a hose into it. The fines will go away with the surplus water. However, not everybody might find this practical. It all depends upon your cirumstances.
Göte

[Maggi Young]

I would wash out the dust by putting it in a bucket and running a hose into it. The fines will go away with the surplus water.

..... and depending where you do this, you could block every drain  in the street.  

[newstart]

Hi thank you very much I am so glad you all told me this. It turns out the first person I met in the builders yard showed me what he thought was granite dust. In fact it was 6mm chips not grantite dust at all. Our chips look greyish still so are most likely granite still but without the dust. In the midlands often granite is the local stone. As I said above it is that type of size around anything from 2mm to 1cm but mainly 3mm x 3mm. Slightly larger than grit.

I am assuming from your answers this stuff is fine in a potting mix at that particle size as its seems you have gone along with my idea ??

Is it equally fine to dig in for planting alpines out?

Also is it okay as granite contains some limestone I think(thats only me thinking this not necessarily true) . Is the lime locked up in the particle not affecting the plant may be? As you can see I am fairly clueless about granite and could have it very wrong!?

I am not expecting a long answer with science so please do not feel obliged to do this unless you have time and want too.

Thanks I should have the drainage questions sorted then!

David , much appreciated!

[ranunculus]

Hi David,
Granite chips can be added to most alpine/rock garden environments and will enhance the drainage (the main criteria) with little detriment. 

[Martinr]

No Lime in Granite David so no need to concern yourself with that one.

[ArnoldT]

There are many 'Organic' farmers that use granite dust to replace minerals used in growing crops.

Always be aware of the danger of inhaled  dust.

[newstart]

Is there any difference in alpine growth with grit or 6mm chippings in a potting medium? What brought about the questions was I cannot purchase grit in a bulk bag or loose delivered. I have no vehicle to go to quarries etc.

Thanks the above would just need confirming. Many thanks again!

[Maggi Young]

I suppose some refer to various materials as  "grit" but as far as we are concerend, the "grit" we use in our potting mixes is 6mm granite chippings.

[David Nicholson]

Not sure I understand the question???

[ranunculus]

Not sure I understand the question???

Just grit and bear it, David.   

[newstart]

Thanks thats great Maggie. The question was merely to check a few things for future. I just thought that horticultural grit(smaller particle) was the one that is normally used by people and so the question about it being in bulk. Maggie points out that this is not done and you use chippings as builders merchants call them. The point being I have to order chippings from now on. Previously I had not used grit so its a learning experience. I write this as it shows I am not asking something twice but confirming other details.

Thanks all for your help invaluable!

[David Nicholson]

Ah! I've read it properly now

I use a smaller kind than 6cm for my potting mix and a slightly larger size (than my smaller kind-if you see what I mean?) for top dresssing my pots. I also use a course sand which has a git content which is a little smaller than my "smaller" kind. Still with me

I buy from a local builder's merchants in 25K bags because I don't have the room to store in bulk.
The course sand I use is labelled "Medium Grit"
The grit I use in potting is labelled "Course Grit"
The grit I use for topping pots is labelled "Horticultural Grit"

By now Dave you are probably utterly confused! Two options for you Dave-you could probably get pea gravel in bulk from a good builder's merchants, and you might be able to get chick grit in bulk from an animal feed stuffs supplier in your area.

[Martinr]

"which has a git content".................................must not yield to temptation