O/T, don't believe everything in books?

[Bush bunny]

I was trying to find out the p.H of volcanic rocks. In one of my very old gardening books it said, tufa was from Limestone. I don't know which volcano that came from do you? I thought the ones I have were basalt based, so probably slightly alkaline to neutral. I always thought limestone was not igneous. I should know anyway, but thought I would see what other's thoughts are.

[klaery]

There is tufa-limestone a sedimentary rock. There is also tuff/tufa an igneous rock. Two different things. Hope this clears it up

[Bush bunny]

Thanks a mill, I only identify tufa with volcanic rocks. I know of Texan holey rocks. They are limestone. I like them too, but very dear, sold on weight.

[thoglette]

I should know anyway, but thought I would see what other's thoughts are.

On these sort of black-and-white issues, Wikipedia is pretty useful

Limestone
Volcanic Rock