The best way to find out the composition of jewellery alloys is to use the CaratScreenPen from Goldanalytix. It measures the carat number of gold within seconds.
Another way to measure the composition of jewlery is by test acids or an XRF instrument. With the test acids it is possible to find out the carat content of jewellery, as well as some other components of the alloy. When analysing with an X-ray fluorescence device, it is even possible to determine the exact qualitative and quantitative composition of the alloy. For private customers, these devices are usually not profitable with prices of 20,000 € upwards.