Hi Andrea, True granite is a very hard dense stone, so I'd go with as fine a mix as possible. The 1:1:1, Portland, fine vermiculite or fine perlite and sand mix will do that. Are you going to paint the stone? If you do there is a very good thread in this forum on how to paint it too. Good Luck.

The planted hypertufa that I made this spring is starting to get green on the upper edge. I'm suspecting that if there's organics in the mix, the moss will happen all by itself.

Mercedes

Someone gave a couple of recipes for various looking tufa a couple of weeks ago. I saved it for future reference.

Here is a link that might be useful: Classes

Moss will grow in different conditions, but needs moisture and better to have acidic soil.It takes time for the tufa to wash out the extra lime (moss killer). Better to start with some moss or the moss milkshake. I've seen a recipe on the Japanese Garden forum : mix clay(potter or natural)with peat moss and water, smear this on the soil or object you want the moss to grow and press moss on it. This will help to grow. I have to try it yet.

I started a Recipes Bank Thread. I believe this can help you.

We never know where knowledge is ;o)

Here is a link that might be useful: Recipes Bank Thread

If you do a Google image search for granite & click on the first item, it brings up a page with 35 different samples of granite. When I click on those, most of them seem to show samples that have lots of black specks in them.

So, to imitate the appearance of granite, I suggest including some Copper Slag grit to supply the black specks.

Also, the more Peat Moss, the more the result has a tan tinge, rather than grey.

For a start, I suggest a recipe like this - 25% Portland, 25% Copper Slag grit, 25 % fine Vermiculite, and the final 25% consisting of varying percentages of Peat Moss and Perlite.

Where do you get Copper Slag grit?

Businesses that sell sandblasting materials should stock copper slag - look up 'sandblasting' in the yellow pages.

This is a grot I made using Kleenblast slag sand, it does have a nice granity look that I didn't capture very well here. The mix was 1:1:1:1 portland/perlite/peat/sand. I think the perlite wasn't sifted so it ranged from powder to chunks as large as a cooked rice grain (short grained - it's plumper :)).

I think if you are looking for this sand you could ask for black sandblast abrasive, the place where I got it had no idea if it was slag but invited me to come have a look at it. It was $5CDN for a 50lb sack at a building supply store. I'm really liking the appearance of it, it has a glossy, black glass look to it.

Here is a link that might be useful: {{gwi:71160}}

I found some at Menard's in the sandblasting supply area. It was a very large Menards I was very suprised. Around $5 for 50lbs. Gave my bowl a dark grey/black look using grey portland, charcoal powder color and the black sand. Really wanted black so I will have to experiment some more.
Paws

Paws 4 slag to 1 portland and about 10% black pigment is pretty dark.