The Karatmeter is a scientific device launched by India-based Titan Company Limited (TATA Group) which uses X-rays to give an exact reading of the purity of gold. Due to its very high precision, X-ray analysis has been adopted by international agencies in India as part of the certification process used to hallmark gold. It is an accurate, non-destructive means of testing the purity of gold and other related elements.
Using this technique, the precise percentage by weight (of karat) in a solid piece of jewellery can be determined in just a few minutes. It also accurately determines the element composition of all types of gold, white gold, platinum, silver, palladium, rhodium and related alloys.
Energy dispersive X-Ray fluorescence technology (ED-XRF) is a simple, most accurate and most economic analytical methods for the determination of the chemical composition of many types of materials. It is non-destructive and reliable, requires very little sample preparation and is suitable for solid, liquid and powdered samples. It can be used for a wide range of elements, from Chlorine (17) to Uranium (92), and provides detection limits at the sub-ppm level.
There are many models of Gold Purity Testing machines available - from portable (light weight) to industrial grade machines.
Apart from X-ray spectrometer technique, other older traditional methods are using the TouchStone and Acid to test the gold purity. But TouchStone and Acid are destructive testing - a tiny sample of gold is cut and then tested. The sample is rubbed on TouchStone and a drop of acid is put on it and the goldsmith observes the residue using a magnifying lens. Based on experience, gold smith can determine purity of sample.
Sample photo of Gold Purity Testing Machine