Gemology Hub | Gemstone & Mineral Identification Guides

A high Mohs number does not answer every question about a gemstone. For everyday jewelry, you also need to think about breakage and the stone's response to heat and chemicals. Moonstone is a feldspar gem that needs gentle care. Photo: Simon Eugster, CC BY-SA 3.0 , via Wikimedia Commons . Image unchanged. Three different questions Property Simple meaning Hardness How well does the surface resist scratches? Toughness How well does the material resist chips and breaks? Stability How does it respond to heat, light, moisture and chemicals? GIA explains these three parts of gem durability in More than the Mohs Scale . Why the Mohs scale is only one clue The scale compares scratch resistance. Its numbers are not evenly spaced. A stone at 10 is not simply twice as hard as one at 5. The number also does not measure resistance to a sudden impact. Can diamond break? Yes. Diamond resists scratching extremely well, but a hard blow can chip or split it. Cleavage describes directions in a crystal...

Moonstone looks beautiful, but cleaning it roughly can cause damage. This simple guide explains how to care for a known moonstone gem in jewelry. Moonstone is a feldspar gem that needs gentle care. Photo: Simon Eugster, CC BY-SA 3.0 , via Wikimedia Commons . Image unchanged. The gentle cleaning method Check the setting first. If the gem is loose or cracked, let a jeweler inspect it before cleaning. Use warm water with a small amount of mild soap. Gently clean with a soft brush. Avoid pressing hard around the stone. Remove the soap gently and dry with a soft cloth. GIA recommends warm soapy water for moonstone. It advises against both ultrasonic and steam cleaners. See the GIA moonstone care and cleaning guide . Why moonstone needs care Moonstone has a Mohs hardness of 6–6.5, but its toughness is poor. Two cleavage directions make it vulnerable to breaking from a hard blow. High heat and sudden temperature changes can also cause breaks. Before wearing a moonstone ring A ring is more exp...