You are quite right that Supply and demand should both be...

You are quite right that Supply and demand should both be considered however i think we also need to weigh short versus long term factors impacting both.

Supply side:
My (somewhat uneducated) understanding is that supply is currently restricted because major mining operations in South Africa have been closed due to turmoil in that region (triggered by the arrest of Jacob Zuma). Maybe this is an overly simplistic view? I'm not sure.
South Africa has long been a troubled region and may remain so but in regards to our purpose the question is how much stability is actually required to keep a functioning mine? If things calm down enough it will reopen.

In the short term supply is restricted but in the medium term this may not be true.

Demand side:
A significant amount of demand seems to come from the Chinese construction industry (no one here has contradicted this assumption). Chinese real-estate is an interesting beast and is acting as store of wealth / speculative investment vehicle for many people in that country who are suspicious of the Chinese stock market. The possible collapse of Evergrande may or may not cause that market to crash which would be disasterous for both China and Australia. If it happened this would cause serious long term impacts to the economies of both countries since it would crash areas of our mining industry that cater to construction in China. It would also hit our Australian realesate prices since there is quite a bit of Chinese investment in Australian housing. That's worst case bear scenario.

The counter argument to the above is that the Chinese Government may step in to save Evergrande. This is likely even though the CCP appear reluctant to help. Also it is possible that fallout from an Evergrande collapse would be more localized that is expected and may not trigger the apocalypse that pundits are predicting. That said if the Chinese housing market is indeed a bubble (there's arguments on both sides) then the CCP stepping to save Evergrande would just be kicking the can down the road, the systemic problems would still be there.

Regardless in the medium term there seems to be a high risk to Chinese demand for mineral sands and this is a significant percentage of global demand.