Chalk verses sand in Lime Plaster/render

[tumbledown]

i've read a few postings regarding mixing chalk instread of sand into the lime putty. It seems to have quite a few benefits over the traditional sand.
I read somewhere about a chap who never uses anything else.

Are there any circumstances where you wouldn't use it? Are there any disadvantages?

If it has only advantages and no disadvantages, why isn't it the norm rather than the exception?

 

[biffvernon]

Chalk would not be as durable so I wouldn't use it for an external render. I think it would be quite easily damaged by frost as water soaks into chalk particles - they are very permeable - and would break them apart on freezing.