The economic value of a commodity is both use and exchange values. You’re talking of use values here. They are included when talking of the value of an object.
You’re also, like other commenters, unnecessarily stuck on the example of gold. See past that. Gold is no different from any other object—anything can lose its value, because that value is the product of human activity, ideas, and relations in a market. When I say If everyone decides gold has no value tomorrow, it has no value, I was talking all value. Your scheme won’t work when everyone decides gold has no value, because gold is nothing more than an object in the market whose value is constructed by human relations and activity.
You’re also, like other commenters, unnecessarily stuck on the example of gold. See past that. Gold is no different from any other object—anything can lose its value, because that value is the product of human activity, ideas, and relations in a market. When I say If everyone decides gold has no value tomorrow, it has no value, I was talking all value. Your scheme won’t work when everyone decides gold has no value, because gold is nothing more than an object in the market whose value is constructed by human relations and activity.