For the Love of Gemstones

Working with gemstones can be a bit of a minefield and it helps to know a bit of background about the nature of the gemstone we are about to use.

Understanding the durability of a gemstone is tantamount to how we decide to set the stone. For example, tanzanite is an extremely fragile gem and not only should it never be put in an ultrasonic cleaner but I would be quite dubious about setting it in a ring where it will undoubtably get caught on things and be generally knocked during day to day use. At a push, if you were to set it into a ring then a rub over setting would give it the most protection but even then there are no guarantees that it will stand the test of time.

Carl Friedrich Christian Mohs, a German chemist and mineralogist developed the Moh’s scale of hardness so that we can have a better understanding of our stones:

Moh’s Hardness Scale:


Absolute Hardness









Fingernail 2.5 Hardness




Copper Penny 3.5 Hardness












Steel Nail 6.5 Hardness








Masonry Drill bit 8.5 Hardness


Corundum (sapphires and rubies)


Note Corundum is twice as hard as Topaz




almost 4 times harder than Corundum

This was worked out on the basis that each of these ten minerals will mark or scratch a mineral with a lower number on the Moh’s scale.

However, we don’t want to test this theory by scratching our gemstones so, here is list of gemstones and what to avoid doing to them (the harness scale is courtesy of Gem-A):


Hardness Scale:

What not to do to your gem:


2 1/2

Heat- Keep it away from heat

-Avoid cleaning solutions as this could affect the colour


-Don’t take a blow torch to it!

-It won’t survive the ultrasonic

Beryl – Emeralds are a major player in the beryl family

7 1/2

-Keep it away from heat as it will make the colour fade, or it could even fracture

-Emerald’s do not like cleaning solutions

-The ultrasonic is an absolute no – a certain death to an Emerald


8 1/2

– Chrysoberyl is usually hardy but don’t aim your blow torch towards it.



Corundum is pretty sturdy stuff, however, if it is heavily included or it has been treated then it will not tolerate heat, borax or the ultrasonic.

When buying corundum, it is worth asking some very pointed questions about the nature of the gemstone you are purchasing so that you know exactly what you are dealing with.

If it is not included, then the stone can sustain heat and the ultrasonic cleaner.



If the stone has been filled or is heavily fractured, then avoid:




However if your stone is not heavily fractured and is of high quality, then it can stand heat and the ultrasonic



-Keep it away from heat

-It can’t withstand exposure to any kind of chemicals

-It will disintegrate in the ultrasonic



Fluorite is a very fragile but pretty stone. It really can’t tolerate anything:

-Heavy handling – it will be risky in some settings where it can’t take pressure to set them.


-Fire – it will not abide by any soldering work once set.

-Any kind of chemicals

-Being knocked

-Ultrasonic cleaning.


6 1/2

Garnet is fairly durable but avoid:


-Abrupt changes in temperature– this is known as thermal shock

– Steer clear of the ultrasonic as it will cause internal fractures in the stone




7-7 1/2

Considering it is a relatively hard stone Iolite doesn’t hold up very well with anything because it is actually a very brittle stone.


You must be very gentle with Iolite otherwise it will break due to its brittleness.


It doesn’t sustain:

-Ultrasonic cleaning

-Chemicals or cleaning detergents

-Thermal shock




Jade is opaque which means it is very difficult to identify fractures which cause it to break. They can be incredibly temperamental especially when cutting within Lapidary realms.


Steer clear of:


-Fire – another to avoid soldering when the stone is in situ.

-Chemicals of any kind

-Don’t put it in the ultrasonic.



Opals are another stone to handle with great care. You can’t even do the washing up if you are wearing an Opal ring because it will become milky as it is a porous stone.


Keep them away from:


-Heat as this can cause it to fracture

-A definite no to and soldering work once set.


-Being knocked

-Avoid the ultrasonic at all costs


6 1/2

Keep away from:



-The ultrasonic cleaner


3 ½ – 4 at best

Pearls don’t like being kept with other members of your jewellery box as they are unfriendly and don’t like being touched by others on account of the fact  that they have sensitive skin and can be easily scratched.


This being the case, they can’t bare anything.


An absolute no to:




-The ultrasonic cleaner would completely destroy a pearl.



Quartz is an odd one as it’s hard but can be easily damaged depending on the quality. If it is heavily included, then proceed with caution.

-If heavily included then avoid the ultrasonic

-It doesn’t like extreme heat and then extreme cold. This leads to thermal shock which can cause the quartz to fracture

-If the stone gets hot then it can also cause the colour to fade

-In summary, keep it away from fire and heat

-If you are planning to put Quartz in the ultrasonic then proceed with caution as a lot of the stones seen on the market over here are heavily included. Again, it is really good to question what you are purchasing.




Spinel are usually pretty strong but again like most stones it doesn’t overly enjoy being stuck in the ultrasonic – be careful here.


6 1/2

As discussed, Tanzanite is a fragile one, therefore, one to handle with a lot of care.

The Tanzanite supply will eventually run out making it rare and in demand, which is likely to push the value over time.




Topaz is hard, but it can fracture so please keep it away from:



-It is a risk to place it within the ultrasonic cleaner.



Things to keep clear of are:


-The ultrasonic


6 ½ – 7 1/2

One of the most underrated gemstones.

Things to avoid are:


-UV light as this can cause the colour to change

– And FINALLY – the ultrasonic

There aren’t many gemstones which can sustain time in the ultrasonic cleaner. Realistically, anything from an 8 and up on the Moh’s scale should be able to withstand the ultrasonic, anything lower and it will always be a risk. Remember to research the quality of your gemstone before proceeding – a heavily fractured stone of any hardness is always risky.

Let’s address the protective pastes that are sold that protect your stone if you need to solder when a stone has already been set. Do they work? The answer is, yes they do. However, they won’t protect certain stones if you have the torch near them for too long. Pearls, Amber, Opal, Emerald and any stabilised stones are unlikely to handle this. Stabilised stone are stones that have been crushed and a resin or glue has been used to put it back together.

In terms of polishing with a polishing motor, you can use it on some designs where a stone has been set, just exercise some degree of caution. The friction build up upon the piece against the polishing mop can get too hot causing your stone to crack or the colour may fade depending on what you are working with. Organic materials such as Pearl and Amber should never go near the polishing motor. Opal is another one which needs to be handled carefully. If you do need to polish around a fragile stone then it is best done by hand. You can put masking tape on the stone to protect it.

Certain gemstones don’t stand the test of time when they are not cared for. Pearls and Opals are the major culprits that spring to mind. Opals should not be put in water as they eventually lose their lovely effect and become milky. Likewise, pearls will lose their lustre over time if they are sprayed with perfume or perfumed moisturiser. You also need to be wary of household cleaning products – they will also affect your stone. It is definitely worth checking how porous your stone is. If it’s porous then it will be easily damaged.

The most porous are:

  • Pearl
  • Opal
  • Emerald
  • Amber

The best settings for the more fragile stones are a bezel/rub over setting as this will give the stone all round protection. In my humble opinion, the two stones that should ALWAYS be set in a bezel setting are Tanzanite and Opal. We see these stones set in claws all the time in jewellery shops. There is usually a cluster of diamonds or something else around the stone. This will give it some protection but not as much as a bezel setting would. Just remember there are many setting styles such as micro settings which look pretty, but the reality is they aren’t actually that practical for wear and are likely to get damaged, this will lead to customer’s returning the design for regular repair, which leads to customer frustration and reduced confidence in purchasing from you in the future.

When it comes to selling your jewellery, you should be able to give some information to your client about not just how to care for their jewellery but how to care for their gemstone too. I can’t stress to you enough how important it is to research the gemstones you purchase. Some gemstones are found in parts of the world which throw up ethical conflict. Your job as a jeweller is to source responsible materials, research your materials and make sure the designs you produce can live up to the expectation of your customer. Make sure you are educated enough on what your are supplying, to be able to educate your customer.

When you start your journey into jewellery making I think that there are definitely stones that you can practice with which are lower risk. Quartz, Jasper and Agates are great to use as they are very hard and relatively inexpensive compared to some other gems on the market but they are also attractive. Take it slow and start building your skills and then consider working with the pricy gems.