I always thought it was a little weird that dark sun was short of metal, but had wood, bone, chitin and the like to spare.
They have plenty of sand, make weapons out of glass.
Anyway, stone weapons are plenty heavy and sharp and every bit as deadly as metal ones. They're just not as durable.
Instituting armor vs weapon type adjustments could give you some added realism to the point(npi) that materials characteristics of weapon & armor could start making a difference.
Item saving throws by material type were a thing in second edition, so this was also built in as well as the attack/damage modifiers which were added for Dark Sun.