How to Clean Your Stone Based on The Mohs Scale

Author Veronica Rose
Date Oct 8, 2021

First things first, we don't expect you to know what the Mohs scale is, so let us explain. All stones are not created equal, some are hard and extremely durable and others are a lot softer and more prone to scratching or damage if not cared for properly. The Mohs scale helps us differentiate between each stone/mineral, their level of hardness and their ability to resist scratching. Hardness is measured from 1-10, with 10 being the hardest - diamonds are right at the top of the list.

When it comes to jewelry care, there is one activity that must be done but creates the biggest opportunity for damage...and that's cleaning. If you're going to own a beautiful stone, it deserves a beautiful shine - but with caution. Steaming a stone or using ultrasonic cleaners are the best way to get that perfect sparkle but if you expose a softer stone to high heat and steam, you could crack or damage it. Yikes! This is why we thought we would create an easy to reference list of the most commonly owned stones, their ranking on the Mohs scale and the best way to clean them.

Hard Stones
Hard stones are going to include diamonds of course, sapphires, rubies etc. and you will have a lot more flexibility and freedom with how you want to clean them. Ultrasonic cleaners and steam are no match for these hard stones!

Mohs Rating: 10
Diamonds rank at the top of the MOH scale because they are extremely tough and durable which means it is the least likely to get scratched - only a diamond can scratch a diamond. Harsher cleaning methods are going to get you the best shine and sparkle but should only be done by  professionals like when you bring jewelry in to Long's for a cleaning. At home, you can clean your diamonds with lint-free cloths, commercial jewelry cleaning solution, and household detergents.

Mohs Rating: 9
Next up on the scale after diamonds are sapphires - another extremely tough stone making it a great choice for daily jewelry wear. When cleaning, you can never go wrong with warm, soapy water. For untreated sapphires, ultrasonic and steam cleaners are usually safe but for fracture-filled, cavity-filled or dyed material, a damp cloth is recommended.

Mohs Rating: 9
Like sapphires, rubies are also scaled at a 9 on the MOH scale meaning it is extremely tough - also great for setting in rings or everyday jewelry. Resistant to the effects of heat, light and common chemicals, rubies are safe to be cleaned with ultrasonic and steam cleaners - by a professional of course. At home, like sapphires and diamonds, it is recommended to use warm soapy water or even commercial jewelry cleaner.

Mohs Rating: 7
Citrine can be safely cleaned with warm, soapy water. Ultrasonic cleaners are usually safe except in the rare instances where a stone is dyed or treated by fracture filling. Steam cleaning is not recommended, as citrine should not be subjected to heat.

Soft Stones
Soft stones are much more prone to scratches and damage so most often warm, soapy water is your best bet for cleaning. Be careful to also keep soft stones dry, and out of contact with hard stones as they scratch easily and can disintegrate. Even sweaty palms can cause a stone to lose its shine. 

Mohs Rating: 7.5-8

Emeralds are considered to be fairly hard but they still need extra care when cleaning because most are fracture-filled. These fractures make it risky to clean emeralds with steam or ultrasonically because the vibrations can weaken the fracture-filled stone and the steam is hot and can cause oil or unhardened resin to sweat out of the fractures. The best way to clean emerald jewelry is with warm, soapy water, or a warm soapy cloth. Do not soak emeralds in soapy water and avoid harsh detergents that might dilute or remove any treatment from the stone. Never soak emeralds in solvents such as alcohol, acetone, or paint thinner.

Mohs Rating: 5 - 6.5
When cleaning opals you should excise extreme caution to avoid crazing. This is what happens when an opal is exposed to harsh heat, direct sunlight or excessive dryness and it loses moisture; this creates a fine network of cracks in your opal that look like a spider web. Solid opal should be cleaned gently with mild detergent in warm water and a soft toothbrush or cloth. Avoid bleach, chemicals and cleaners. Doublets & triplets may be wiped with a damp soft cloth and mild detergent, but should never be soaked or immersed.

Mohs Rating: 5-6
A turquoise hardness is generally fair to good which means it is a softer stone that requires caution while cleaning. Some turquoise stones can actually be made with composite pieces which mean smaller pieces are bonded together to form larger pieces. This makes for a beautiful looking stone but it also makes them fairly unstable when exposed to harsh treatment. The best way to clean a turquoise stone is with warm soapy water and to avoid hot steam and ultrasonic cleaners. Because some turquoise stones are heat treated to improve the appearance of its surface, using heat or any type of chemical solvents to clean it can cause discoloration or damage to those treated surfaces. Even cosmetics, perspiration or skin oils can cause some damage so be careful!

Mohs Rating: 2.5
Ranking very low on the MOH scale, pearls are very soft and can easily be scratched or abraded meaning they definitely need some extra care and attention when cleaning. High heat can burn cultured pearls or cause discoloration, splitting or cracking so they should never be cleaned in an ultrasonic or steam cleaner. Pearls also have a natural nacre that can be easily removed or cracked by intense light or chemicals so it is only safe to use warm, soapy water for occasional, thorough cleaning. If the pearls are strung, be sure the string is completely dry before wearing. For more daily care, we recommend regularly wiping cultured pearls with a very soft, clean cloth after each wear.