It's quite an interesting question! Silver on one side, would contain material such as copper, gold,zinc and much more, and the conductivity between these would be in the range of 16-98. But as for the lead's conductivity, they would be between 1 to 9, containing mercury,tin, and nickle, and also much more. Now, we would think, what does the word conductivity even mean. Well, this would indicate how each mineral would handle heat. It would either do two things, it would either expand, or conduct. And that would be how the mineral's about would handle heat. That's why they are compared.