IMHO we definitely need some additional types of materials. At least one more for the start.
And recycling Debris would also be great thing to have.
Another idea I might suggest is obtaining metal through trade. Imagine that you have colonists with arts skills - allow them to... say: manufacture sculptures or jewellery consuming 1-2 metal units that can be sold to traders for ~5 metal units. Proper balance of time would be required, but if colony got enough members - it could allow it to sustain itself without endlessly digging through all of the mountains. Of course this can be expanded to a whole crafting system and live supply/demand economy (more you buy = higher prices. More you sell = lower prices).
And recycling Debris would also be great thing to have.
Another idea I might suggest is obtaining metal through trade. Imagine that you have colonists with arts skills - allow them to... say: manufacture sculptures or jewellery consuming 1-2 metal units that can be sold to traders for ~5 metal units. Proper balance of time would be required, but if colony got enough members - it could allow it to sustain itself without endlessly digging through all of the mountains. Of course this can be expanded to a whole crafting system and live supply/demand economy (more you buy = higher prices. More you sell = lower prices).