Jewellery Care by Gemstone Hardness: The Mohs Scale Explained
The safest way to clean a gemstone is decided by more than how hard it is. Hardness tells you how easily a stone scratches, and the Mohs scale ranks that from talc at 1 to diamond at 10, a system the USGS traces back to the Austrian mineralogist F. Mohs in 1822. But hardness says nothing about whether a stone will survive an ultrasonic bath. Topaz sits at 8, harder than most stones in your box, and GIA still says to keep it out of steam and ultrasonic cleaners. This guide covers both halves: what scratches what, and what actually...
