Karatage of gold is tested using gold testing kits. These kits contain various tools, but the usual content is a set of test acids, a set of test needles, and a touchstone. You may also need to wear gloves during testing to protect your hands from the acids. Magnets and loupes can come really handy.


You can do better testing with a touchstone which is a black stone with a somewhat rough surface. You rub gold against the touchstone until you see a golden streak on the black surface. You drop the corresponding acid. There should be no reaction if the gold has the right karatage. If the streak fades under the drop of acid then it contains less gold than the embossed marking says. https://www.a1mint.com/shop/