DD>> I remember that when my kids were small, we always got our sand for  the 
kids'
DD>> sand box from the building centres (homes, not plants) and it  was 
always Silica.
  >>..., beach sand is rounded (moresore from the ocean) andwill pack down
  >>very hard causing poor drainage.
This is true, ... if it is on the beach, in a sand box, or the like... but it 
will only improve clay soil! (...could it *get* any worse?   :)
 DD> ... I live on the shores of LakeOntario...freshwater...thus freshwater 
sand.
I say, again... (natural) sand is *always* silica... but not all silica is 
sand.  It doesn't matter if the sand is of the kind that packs (in and of 
itself...) because it is not going to be with "itself", but with clay and 
compost.  I asure you that if you have clay soil and wish to break it up  
(use sand... *any* [non-saline] sand) and *keep* it broken up (use compost... 
any kind of compost!).  *And* keep turning it... and turning it... and 
turning it...  (part of the secret of getting it to a "friable" state!)  
*Also*, use the weather.  Freezing is one of the *best* of tools for this!  
(And, it's *free*, for many of us!  :)
cheers,
WL Sakowski
---
---------------