Here you can see the minerals previously stored and sell them if you decide to do so. It is probably better used as a buffer for fulfilling any long term contracts that you have agreed to undertake.
The contracts screen has yet to be designed.
In theory selling a large quantity to the market will decrease prices because of the laws of supply and demand but you need to have a very large quantity to make a serious dent in the market, or change any underlying sentiment.
Any minerals sent to storage will have a fixed cost based upon the quantity stored.
Any comment welcome at firstname.lastname@example.org