Last updated on May 8th, 2023 at 11:14 am
Gem quality rubies that have not been heat-treated to intensify the color are quite rare. The bigger the ruby, the more value per carat.
For reference, 5 carats equals 1 gram of weight.
If you have a ruby that is more than 1 carat that has never been heat-treated, has great color quality and has been expertly cut top and bottom, the value will go up.
For example, a 7 carat ruby with deep color and plenty of light transfer could value upwards of $25,000 per carat, or more than $175,000 for a single stone.
Rubies and Sapphires
Rubies and sapphires are actually made up of the same mineral, corundum, formula Al2O3.
The only difference between a sapphire and a ruby is that rubies are red stones of gem quality.
You may own or see gems that are referred to as “pink rubies” but these are actually sapphires.
Fundamentally, if it isn’t red, it’s a sapphire.
Corundum is formed in slow cooling igneous rock. What makes rubies so rare is that corundum has to form in rocks that have no silicon and lots of aluminum.
Silicon is one of the most abundant minerals on the planet, so the chance of forming rubies in the earth’s crust is actually pretty slim.
Rubies Are Tough
Rubies are incredibly hard. In fact, Corundum is the third-hardest mineral on the earth, just behind diamonds and moissanite.
The trick to working with rubies to encourage the most light possible through the stone requires the lapidarist to design the initial cuts to remove as little material possible while promoting the most light transference.
This work includes clamps and hardware to hold the gem in place, tools to make the cuts and finer grinding tools to smooth the surface.
The technology to polish and improve the look of rubies has expanded over the years.
While this cannot be fully mechanized, the tools necessary to make precise cuts have increased in precision and accuracy.
If you have an older ruby that is rather dull or dark, it could be that the bottom of the gem has not been cut or polished to best effect.
Consider taking the piece to a gem professional for an assessment; a bit of improvement on the piece could make a radical change in the look of the stone.
Other Ways to Change the Look of a Ruby
A common way to change the color and appearance of many gemstones is to apply heat. Heating a ruby can deepen the color and make the stone appear more smooth.
Do be aware that this heat application could also lighten the stone or remove the natural fingerprint of the stone.
If your ruby formed with a small inclusion, such as another mineral or a tiny fracture that makes it unique, heat may take that away.
If you’ve had a ruby valued and are considering getting it heat treated, talk to your valuation professional to make sure that you won’t devalue your stone.
Fans of natural gems appreciate the tiny inclusions that make the stone unique and original.
Unless you can be sure that heat treating your ring will get you the shade that you want, avoid heat-treating an existing stone.
Ruby Mining Today
Currently, rubies are mined in
- Sri Lanka
If you are considering buying a ruby from any of these regions, make sure that you buy it from a reputable gem dealer and consider getting your gem checked out by another jeweler or gem dealer.
In addition to a large concentration of real rubies, there are an awful lot of fraudsters working in the region.
Buying Smaller Rubies
Rubies under 1 carat that have not been heat-treated will be a bit cheaper per carat than rubies over 1 carat.
Depending on the lapidarist, the number of facets and the polishing requirements, you should be prepared to spend between $4,000 and $5,000 per carat.
As a general rule, factors that impact the price of a finished ruby include
- color: an intensely red unheated ruby will cost more
- shape: round and oval cuts are generally cheaper than square cuts
- level of inclusions: fingerprints can add to the value
If you don’t want a stone with a lot of inclusions, consider getting a cluster or pair of small rubies that have had the inclusions polished away.
Be ready to do your due diligence; if you find that your chosen ruby has been heat treated despite your wish to get an untreated ruby, someone up the supply chain has either made a mistake or chosen to try to deceive the next buyer.
Gems pass through many hands before they are placed in your chosen setting.
For high-end jewelry, it is critical that you know your jeweler and that they trust their supply chain. A good jeweler can protect you from loss due to fraud.