Identifying metals in jewelry coins or antiques by cth

Author:cth
Language: eng
Format: mobi
Publisher: CTH
Published: 2009-10-05T04:00:00+00:00

Doing hardness test

You will need a few things first:

Lead fishing weight

Sterling silver such as a piece of jewelry

Aluminum can or aluminum foil

Piece of copper (penny made before 1982 or piece of copper tubing will work)

Iron file

These are common easily obtainable items you can use to test the hardness of a metal. You can obtain these and cut or shape them into a point for testing.

By looking at the hardness column in the chart below you can use the scratch test to narrow down the metal type. Metals in this column will only scratch metals listed below it. Aluminum would scratch gold or silver but not copper.

Suppose you have some connector contacts you suspect might be platinum or palladium but you don't know. Looking at the chart below you see that nickel is softer than palladium but harder than platinum. Since iron is the same hardness as nickel on the list use your iron file to scratch the contacts. If it scratches the contacts they can't be palladium because palladium is higher up on the list than iron and therefore harder than iron so an iron file cannot scratch palladium.

Now use your piece of copper to scratch the contacts. Since platinum is higher up on the list than copper, copper cannot scratch it. Therefore the metal is probably platinum plated. It's like Sherlock holmes, eliminate the obvious and whatever is left has to be the truth.

Using hardness we have not identified a metal but have eliminated any other metal it might be. The only metal on the list that can be scratched by an iron file but not a piece of copper is platinum

Now that you think the metal is platinum you can do another test. First you will need to go to the hardware store and by a torch head and some gas cylinders that burn at different temperatures - butane, propane, map gas etc. They are cheap and a good investment. Look on the side of each cylinder and it will tell you the temperature of the flame the gas produces. The chart shows platinum melts at 3200 degrees f and palladium at 2830 degrees f. Choose a gas that burns around 3000 degrees. If it won't melt the metal this backs up your hardness test that the metal is platinum.

The chart below shows metals listed according to their properties going from highest to lowest. In the hardness column the hardest metal is at the top and they get softer as you go down the list. Specific gravity column has heaviest metal at top and they get lighter as you go down the list. Melting point has metal with highest melting point at top with the melting point getting lower as you go down the list.

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