Smuggling sand - that's a new one!
I would imagine that the laws of Egypt (or whatever other country in other cases) would prohibit the removal of sand from the country; is it really that interesting?
It would definitely be a disease risk and come under scrutiny by Aussie customs officers; I'd imagine it could cause trouble in the US or other countries, but check the local customs rules.
Why not just have some in your sneakers?
It's not like you really need to bring too much, right?