I didn't say a material replacement necessarily offers equal or superior properties. I said compromises can be made in design and circumstances for material use can change. Those changes aren't restricted to engineering expectations. Sometimes, a material becomes more expensive than it's worth, for example, and a compromise is made. The material can also become the target of government regulation, making it less useful for an application. When those circumstances become adverse enough, nobody wants the stuff and its value becomes zero. Please see asbestos and DDT.

There are many, many other examples, including those that fell out of use due only to changes in technology. If, for example, our technology moves on from electrons to particles or radiation that aren't affected by electrical conductivity (which is taking place), the demand for gold as a conductor will eventually drop nearly to zero.

I didn't say a material replacement necessarily offers equal or superior properties. I said compromises can be made in design and circumstances for material use can change. Those changes aren't restricted to engineering expectations. Sometimes, a material becomes more expensive than it's worth, for example, and a compromise is made. The material can also become the target of government regulation, making it less useful for an application. When those circumstances become adverse enough, nobody wants the stuff and its value becomes zero. Please see asbestos and DDT. There are many, many other examples, including those that fell out of use due only to changes in technology. If, for example, our technology moves on from electrons to particles or radiation that aren't affected by electrical conductivity (which is taking place), the demand for gold as a conductor will eventually drop nearly to zero.

I didn't say a material replacement necessarily offers equal or superior properties. I said compromises can be made in design and circumstances for material use can change. Those changes aren't restricted to engineering expectations. Sometimes, a material becomes more expensive than it's worth, for example, and a compromise is made. The material can also become the target of government regulation, making it less useful for an application. When those circumstances become adverse enough, nobody wants the stuff and its value becomes zero.