Ruby: Natural or Synthetic?

Posted on 15/08/2019 by Steve Waddington

A friend sent me a ruby to help assess the value a parcel they were considering as an investment. On first glance it looked like a very nice gem, but all that can be said about it at that stage is “it is a red transparent stone”. The parcel was reported to have come from the Luc Yen mines in Vietnam, a source of exceptional rubies and spinel.

The first step is to determine if it is actually ruby. A minute or so with the refractometer revealed an RI of 1.762 to 1.77, as expected for corundum. It’s birefringent nature was verified under the polariscope, with a lovely uniaxial figure. No more testing needed here, it’s clearly corundum.

Next is to look under magnification. Under a 10x loupe, the gem is remarkably clean, there are no inclusions to be seen at all. This is either an exceptional natural ruby, in the order of $10,000 per carat, or it is a synthetic worth tens of dollars per carat. One point of note is that the girdle was not polished and many of the crown facets were misaligned. Generally I would expect a top value ruby to also have excellent facets and finish.

Under higher magnification, 30x, the gem was still essentially flawless. However, under diffuse lighting curved colour banding could be clearly seen. Curves simply don’t appear in natural corundum, but are a common feature of synthetic gems made with the flame fusion process.

These photos were taken with a Canon DSLR and 100mm macro lens. The ruby is 6.5mm in circumference and the optics are pushed to their limits to get an image at about 25x magnification. Nevertheless, the features are clear enough to be made out, though they are much more obvious under a microscope. The white spots are just specs of dust on the surface.

fig2: Diffused light shows curved colour banding

At this point there is no doubt it is synthetic ruby. A very nice gem, but worth maybe $30 at most.

Natural Ruby Cabochon Factory 2nds

Posted on 09/08/2017 by Steve Waddington

Natural ruby with no heat for $15 per carat.

Over 300 pieces of natural ruby cabochons. No heat or any treatment. These are factory 2nds and all have eye visible surface defects and inclusions.

Weights are from 0.3ct to 29ct.

I will sell these for $15 per ct, or make an offer for the whole parcel.

Photo taken at midday with natural light.

Medium Dark, Strong to Vivid Ruby

Posted on 26/07/201726/07/2017 by Steve Waddington

Ruby mined Madagascar and cut in Bangkok is showing excellent color.

These are some of the latest cabs from the Madagascar rough ruby bought last year.

Ruby Cabs Medium Dark to Dark Tone with Moderately Strong to Strong Saturation — Ruby Cabs, Medium Dark to Dark Tone with Moderately Strong to Strong Saturation

Ruby Cab variations light to dark tone — Ruby Cab variations, light to dark tone

These are straight from the mined rough, with no heat or other treatment.

How do you like your coffee? Dark and strong, like my rubies.

We can cut to any shape/size and calibrate to 0.1mm tolerance.

Gold Sheen Sapphire and Ruby in Mens Jewelry

Posted on 25/07/201725/07/2017 by Steve Waddington

Gold sheen sapphire and dark, vivid ruby is ideal for men’s jewelry.

Typical design styles for men’s jewelry use flat mountings with large(er) size gemstones. This requires a faceted gem with a larger table size, or flatter cabochon that presents well, which favors opaque over transparent stones.

For example, this gold sheen sapphire ring has a 45ct stone with a 22mm x 16mm table. The faceting picks up brass, copper and gold tones as light plays across the surface.

45ct Gold Sheen Sapphire Men's Ring — 45ct Gold Sheen Sapphire Men’s Ring

The rubies in these rings are cabbed from the same piece of rough ruby. In larger sizes, the dark tone with strong saturation is great for men’s rings, yet still beautifully feminine in smaller sizes.

20ct and 10ct Mens and Womens Ruby Cabochon Rings — 20ct and 10ct Men’s and Women’s Ruby Cabochon Rings

What is a Ruby?

Posted on 22/07/201722/07/2017 by Steve Waddington

What are the criteria that gemological institutes follow to determine if a sapphire is a ruby? Can there be pink rubies?

The process to determine a ruby is straightforward:

Is it corundum? If no, not ruby, if yes then:
Is it red? If yes, then ruby, if no then it is sapphire

There is no pink ruby, pink corundum is called pink sapphire. Any colour of sapphire that is not blue is generally known as fancy sapphire.

However, what is ‘red’ and when does light red become pink? Is reddish orange still red, etc is a matter of individual opinion. Both hue and tone have to be taken into account.

This is a colour hue chat:

GIA Hue Chart — Hue Chart used in GIA Color Gemstone Grading

As you can see, there is no ‘pink’. Pink is a lighter tone of red.

This is a tone chart:

Gemstone Tone Chart — Gemstone Grading Tone Chart

To make it confusing, tone is often referred to as saturation. While this chart says ‘saturation’, what it is really showing is tone:

Not a tone chart — Chart uses ‘saturation’ where it means ‘tone’

So when grading a stone as ruby rather than pink or fancy sapphire, it needs to be ‘red’ with medium or better tone. Subjectively, one grade difference is acceptable – what I might call ‘red’, you might call ‘slightly purplish red’, or what I might call ‘medium’ tone, you might call ‘medium light’, and that is ok.

But there is no absolute definition for ruby, some labs might class ruby as anything with red in it, others might say red only, or some might include orangish red and slight purplish red.

Just to be clear about ‘saturation’, the saturation scale as defined by the GIA goes from ‘brownish’ to ‘vivid’ for red gemstones. It should make no difference to the actual classification of whether a gem is ruby or not.

Confusing, right? Yes, at first. But once you get your ‘eye in’ for ruby, you can pretty much tell at a glance. A definition I like to use is that if corundum can return a red ‘flash’ (a property of ruby is it returns more red light than it receives), then it deserves to be called ruby.

This is a sample of ruby colour variation:

The best possible colour of ruby is called ‘pigeon blood’, but that is a whole other story.

Ruby Catalog

Posted on 20/12/201620/12/2016 by Steve Waddington

I have been working on cataloging and publishing a catalog for ruby cabs from the parcel of rough ruby we bought earlier in the year. I was thinking about using a simplified grading system that groups colour/finish/proportions into one metric called ‘appeal’, but it soon became apparent that it would not be workable. Instead I have used the GIA grading method. After consideration, it can’t really be simplified or improved on in any helpful way. And no need to reinvent the wheel.

It took a couple of days to develop the framework for the spreadsheet, going through several iterations before I was happy with it. The version I am running with will auto-generate a long form description from the grading information. I can then just cut and paste that into the description field of the product on the website. I was quite proud of that little bit of spreadsheet scripting, until someone expressed disappointment that it didn’t just automatically post to the website instead of having to manually cut an paste. Alas, the skills for that type of coding left me long ago. Nevertheless, I am pleased with the functionality of my catalog spreadsheet as it is.

Given a base price for the ruby, the spreadsheet will also generate a price. That part still needs a little bit of work, but basically it works on giving a high value to the ‘sweet spot’ of hue, tone and saturation, with modifiers for clarity, finish, proportion and treatment. The base price I take from the average street/negotiated price I see in the market for unheated ruby cabs.

The end result looks like this:

Which gives me a price from $38 to $128 for the best colour/finish grade stones. Market pricing for ruby cabs at the moment starts at $5 per carat for heat/glass filled, $20-$80 for heat treated and $50-$150 for natural/no heat.

The autogenerated description looks like this:

Autogenerated description from grading data

It will be easy enough to replace the commas with line breaks using a text editor if I want the formatting to look better on the product web page.

Now, I know what you are asking. What about the rubies themselves? They are much more interesting to look at that a spreadsheet, after all. So here is a sample of some we have photographed so far:

The next task will be to take the spreadsheet and publish it as a catalog table on the website. That should be straightforward, and I can include a thumbnail of each gem as well, which will link to the full size picture. I expect to have that completed pretty soon.

In the meantime, if you would like more information on the any particular piece, or for rubies in general, just email me at steve@sjwgems.com.

New Factory Cuttings – Ruby

Posted on 02/11/201602/11/2016 by Steve Waddington

I have just seen the latest cuttings from the factory for ruby. We are getting more range of colour and gradings as we progress into the parcel.

Tray of ruby cabochons — Tray of ruby cabs sorted by colour grade

Tray of dark ruby cabochons — Tray of darker ruby cabs sorted by colour grade

I am seeing quite a lot of medium-light and slight purplish red natural unheated ruby cabs in the market now, between $200 and $300 per carat. The lighter stones we are getting from the parcel would match that grade.

Some, like these, are at the other end of the tone scale with strong purple red to purple/red hue and strong saturation:

But I have to say, I do prefer the medium/dark tone best of all:

Medium Dark to dark Ruby cabs with moderate to strong saturation

SJW gems can supply ruby cabs in calibrated sizes to any specification. We own the rough and control the production through to the final polish and shipment. We can accommodate order sizes up to 10,000 carats per month, and welcome small orders from collectors and independent designers. Talk to us now for your Christmas Season orders!

Quick Guide to Buying and Investing in Ruby

Posted on 20/10/201620/10/2016 by Steve Waddington

Some tips and advice for people interested in buying or investing in ruby in the longer term. The main things to consider and avoid.

Ruby is one of the ‘big three’ of precious gemstones – Ruby, Sapphire and Emerald. At one time these were the only types of gems considered ‘precious’, and everything else was ‘semi=precious’. The finest ruby is worth more than diamond, but you can find ruby from as little as $5 per carat (not that you would want to buy it though).

Natural Ruby – For investment purposes, only ever buy natural ruby. Manufactured ruby looks good and is fine for less expensive jewellery, but as an investment it has no long term appreciative value.

Ruby Ring — 1 ct Ruby gold ring. Natural ruby with mild heat treatment.

Glass Filled Ruby – When buying natural ruby, absolutely stay away from glass filled ruby! I can not stress this enough, There is a lot of glass filled ruby around at the moment and you can usually tell because it sells for under $10 per carat. Glass filled ruby is not a permanent treatment, and the gem will deteriorate quite quickly over time. When it is new it is hard to spot, but after even as little as a few months the gem starts to become cloudy as stress fractures build up in the glass.

Heat treatment – Heat treatment of ruby and sapphire has been around for hundreds of years, and is so common that the GIA advises that unless you have certain knowledge otherwise, assume your ruby is heat treated. When done properly it improves the clarity, colour and appeal of the gem. However, there is some risk that ‘heat treatment’ may be used to describe a gem that has been glass filled (which is a type of heat treatment). Unless you know what to look for or are buying from someone you trust, avoiding heat treated ruby will ensure you are not getting an inferior glass filled gem. For an excellent article on heat treatment, see A Brief History of Heat: Heat treatment of ruby & sapphire by Richard W. Hughes.

Other Treatments – Generally all related to heat treating, other processes can include the addition of chemicals to penetrate or coat the gem and improve the colour and fill in any surface flaws. When a coating is applied it is called ‘diffusion’, and if the coating gets scratched or damaged, the appeal of the gem will decrease. Irradiation is another surface treatment where the gem is exposed to beryllium. This is a temporary treatment that will improve the colour, but soon wears off. These treatments are detectable in a gemological lab and always decrease the long term value of the gem.

The four ‘C’s – Cut, Clarity, Colour and Carat size apply to rubies just like any other gemstone. Large carat rubies (over 4 carats) are particularly rare. There is an excellent guide to the frou c’c of rubies at ringspro.com.

Unheated – For any given quality, unheated, natural ruby commands the highest price. A 10x jewelers loupe is usually sufficient to tell a gem with heat treatment from an unheated one. For investment purposes and longevity, nothing will surpass unheated natural stones.

ruby-cabochon-1-3ct — Unheated natural ruby 1.3ct

ruby-cabochon-1-91ct — Unheated natural ruby 1.9ct

ruby-cabochon-2-0ct — Unheated natural ruby 2ct

ruby-cabochon-large-16-35ct — Large unheated natural ruby 16.35ct

Types of Ruby Cuts – Rubies can be faceted or cabbed, both are beautiful. Generally the best stone is used for faceting,while more opaque and darker stone is used for cabochons. Hence, faceted ruby usually has a higher price per carat than cabochon. However, ruby cabs will sometimes have a star phenomena, caused by needle like inclusions of rutile. The more prominent the star, the better. Like sapphire, ruby will have a six arm star, or sometimes, very rarely, a 12 arm star.

If you have more questions about buying or investing in ruby, email me at steve@sjwgems.com, I will be very happy to help you.