Here you can see the current prices of minerals. As in real life these prices will vary due to demand and supply. There might be a large number of discoveries in a specific mineral so the price will start to reduce. If mines of a mineral are fully exploited and closed then there might be a shirtage and prices will enerally rise.
There will also be a link to view historical prices.
Any comment welcome at s.rush@espsoftware.co.uk