Tools to differentiate silver from molybdenum

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bluemoonKY
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I remember reading on a blog or a news article on the internet once that sometimes counterfeiters have made fake silver coins and silver bars out of molybdenum. Silver is worth far more than molybdenum. Counterfeiters made fake silver out of molybdenum because they could acquire the molybdenum for a low price and then sell the molybdenum at silver prices. The source said that the electrical and thermal conductivities of molybdenum are far different than the electrical and thermal conducitivities of silver, and that is how one can use certain tools to differentiate silver from molybdenum. I cannot find the old source on the internet.

What tools can be used to differentiate silver from molybdenum by looking at thermal and electrical conductivities?
 

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To test the resistivity would require a 4 terminal resistance meter, two far terminals to inject a current, with the two closer terminals to measure the voltage drop proportional to resistivity.

You might drop or roll a coin through the poles of a strong magnet. Conductive material will fall slower than a resistive material due to higher eddy currents in the good conductor.

There are electro-magnetic gauges, (NOT ultrasonic), used to measure the thickness of steel plate from one side. Maybe they will give a significantly different reading for a fake coin.
 
Silver is diamagnetic, molybdenum is paramagnetic. So maybe you could measure the detuning of a resonant circuit, when a coin is brought into the coil.
 
DrDu said:
Silver is diamagnetic, molybdenum is paramagnetic. So maybe you could measure the detuning of a resonant circuit, when a coin is brought into the coil.

Could you translate the second sentence in a less technical way please? I don't know what measuring the detuning of a resonant circuit even means.
 
bluemoonKY said:
I don't know what measuring the detuning of a resonant circuit even means.
An inductor has an inductance, L, and a loss or Q determined in part by the core material.
If you have a free running LC oscillator and pass the coin through the coil there will be a change of oscillator frequency. The degree of change will discriminate between the two metals. It is like a simple metal detector.
https://en.wikipedia.org/wiki/Electronic_oscillator#Feedback_oscillator