Glass and iron
One problem on Mars is the high Fe content of the surface soils.
Iron darkens glass, making it hard to get clear panes in thicknesses needed for the armoured roofs that Stephanie has so beautifully painted from Gary's designs.
There may be deposits of low iron-high silica sand on Mars, of course, and finding these will be part of the challenge.
Hopefully they will be more common than gold, or diamonds.