The message
from green earth contains these words:

It is much better to use horticultural grit as it will not contain
huge amounts
of lime. I don't think builders sand contains chemicals but you
should be aware
of the ph (acidity) level of the sand. Some plants tolerate high lime
level
whereas others will not.

Most builders' sand is silica, and should have no pH value at all as it
is to all intents and purposes, insoluble.

I suppose there is a possibility of some sand from local non-commercial
sources containing limestone, and/or oxides of iron.

Some beach sands can't be relied on either: for instance, there is a
beach on Skye which is made up almost entirely of coral fragments.

Generally though, you can be pretty sure that sharp sand can be added to
any (rooting) medium without it altering the pH.

--
Rusty
Open the creaking gate to make a horrid.squeak, then lower the foobar.
http://www.users.zetnet.co.uk/hi-fi/