There should be coal in the Toscana, iirc.
But essentially commerce is a crucial part of the game. The F4, F11 screens are often no big help in assessing incomes correctly. Often it is cheapest to buy, as opposed to produce yourself. The tricky part is to secure a steady flow of supply and in return a reliable income by selling your own goods. Spoiler alert! Building commerce ships can never be a wrong decision.
Should be no problem with silk, though.