Gold isn’t the only metal you might find yourself in a position to buy. You may find yourself confronted with people wanting to sell platinum. Use this guide to learn the ins and outs of testing platinum. When you are testing for platinum, you will approach the process in much the same way you would with testing gold: you’ll use the testing stone again and use acid to determine the metal content of the piece you are testing.
One thing to pay attention to and be aware of before testing for platinum is that iron and steel items will pass the streak test for platinum so before attempting a streak test, you should always start by testing any suspected platinum with a powerful magnet.
If the metal is attracted (strongly) to the magnet, it can be one indicator – but Cobalt is sometimes present in 950 platinum so its not a defining test.
Once you have ruled out steel and iron, take the item and scratch it along the surface of the stone like you would with any piece of gold. Make sure that you have a thick and visible deposit line that you can test accurately and is about 1 inch long.
Apply a drop of your platinum testing acid across the streak on your testing stone.
Identify the reaction. If the metal you are testing is platinum, the streak should keep its bright white coloring for over a minute of exposure to the testing acid.
Be aware that other than iron and steel, there are plenty of other white non-magnetic metals that will give false platinum reading like chromium cobalt, dental materials, some class rings and some metals frequently used in stainless flatware. Always try to verify your results in more than one way whenever possible.