What makes any precious stone/metal/mineral (gold, silver, diamond, sapphire, ruby, etc.) valuable? People want them for various reasons. They want them desperately enough they are willing to pay for them. Rarity also plays a role by the basic rule of supply and demand. Imagine the value water could hold if it became rare. I wonder how much more is paid for water in arid areas as compared to here in the US for example. I recently spent about $5,000.00 to dig a new well and except for the cost of the electricity to pump the water and maybe an occasional pump repair/replacement, that is about the only expense I will have for probably the rest of my life. Essentially, my water costs me almost nothing. I'm betting that is not the case in other places where water is not so abundant.