Metal ore is a resource that can be obtained by mining the large rocks that spawn in the world.
The actual specific details on what resources spawn where and how are not yet fully understood.
What is known, all resource spawn rates are linked. Meaning that if you only gather metal ore and leave all other resources be, eventually there will be no ore spawning.
A furnace is used to refine ores.
This is done by adding wood or low grade fuel plus the ore to the furnace. Ignite it and the ores will slowly start to turn into metal fragments. The yield per 2 metal ore is between 3-8 metal fragments with an average of 6 metal fragments.
Classification : Resources