How accurate are gemstone testing kits?

Basic home gemstone testing kits are moderately accurate for telling diamonds from common lookalikes, like cubic zirconia, but they are quite unreliable when someone tries to pin down coloured gemstones, lab-made synthetics, or more complicated gem treatments.

Most consumer thermal tools, or electrical conductivity testers, cannot truly sort out a natural gemstone from a lab-created synthetic that shares the same chemical properties. Professional gemmological labs rely on advanced spectroscopy, X-ray fluorescence and high-powered magnification, so they can identify the species, the origin and even any artificial enhancements with better confidence, which is why professional certification matters a lot for high-value stones.