Sapphire – Septembers Birthstone Part 3

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Fine Pear shaped Sapphire

Sapphire – Part 3

Welcome to part 3 of our, non scientific guide on looking at blue sapphires. We are going to start off with a little story. The encounter  follows a flow of conversation that I have seen literally hundreds of times working with staff, and clients, at our gem parties.

Story of A Gems Sparkle

It’s a beautiful autumn day and our gem party has just begun. The weather outside is perfect, with a slight hint of fall in the air. The atmosphere inside is festive, and upbeat music is playing in the background. The air is filled with the aroma of hot apple cider and the treat table is decorated with everyones favorite snacks.

Our first client walks through the door. It’s Mary, a real favorite of the store. She is here on a mission to look at some of our finer sapphires. Mary has been in before, but was never quite satisfied with the sapphires that she had seen. The stones were either too dark or too light or too something.

After a quick trip to the snack table, she settles in to look at our many trays of sapphires. We bring out one sparkling tray after another and casually ask her.

“When you look at this tray which gems literally jump out at you? You won’t have to think too hard because the gems will literally call your name.”

While this is all done, tongue in cheek, there is a method to the matter.

“Oh my gosh” she exclaims. “They are all so beautiful, but I in particular love the sparkle of this round one and yes the oval lighter colored one too.”

Fine, Sri Lankan Sapphire, 1.78ct

In the end she makes her selection from about four gems, and narrows it down to a fine medium blue, 1.78ct oval that has a slight violet under-tone. The gem is about $2400.00 over her budget, but because she is so taken by the gems beauty, she finds a way to secure the gem. After all this will one day be passed on to her grand daughter.

So what just happened and why did she pass up on the technically, more valuable gems that were over 2 carats and select a slightly smaller gem?

The Cut

The answer is often in the cut and the resulting sparkle. If you place two 8×6 oval sapphires next to each other, and one weighs 2.34ct and the other one 1.78ct, technically if all else is equal the larger gem should be considerably more valuable, right? Yes, however it may not be the most beautiful, and that is often because of the cut. This is because every variety of gem materials has what’s called its critical angle.

The critical angle is the angle that when the light enters the gem and refracts, that it either reflects back up through the stone and out through the table, or it is transmitted out through the back of the stone.

When the light reflects off of the back facets and up through the gem to your eyes, it’s called sparkle and we love it. When the light travels out through the back of the stone that means it doesn’t sparkle and in most cases it is called windowing.

 

Notice the gemstone above. It only sparkles on the outer edges, due to the fact that most of the light is refracting out through the back of the gem instead of reflecting back to the eye. Cuts like this one are often referred to as ‘native cuts’. This is due to the fact that in most cases, cutters in source countries, are paid by the weight of the gem and not for its beauty.

 

The video above shows what a beautifully proportioned oval sapphire looks like. Every facet is placed with the emphasis on reflecting the color and brilliance back to the eye.

This sapphire was faceted too shallow allowing light to leak out the back instead of being reflected back through the top of the gem.

This pair of sapphires sparkles through and through. That means that it was faceted at an angle greater than 35 degrees, for maximum light return.

Looking at the same pair of sapphires from the side, you can see how the proportions are within the desired angles for maximum brilliance.

 

 

 

 

 

 

 

 

 

 

As you can see in the examples above, sapphires need to be cut to very specific angles. The critical angle for sapphire is around 35 degrees. Since sapphire rough is sold by weight, doesn’t it make sense for the cutter to cut the heaviest stone possible? Of course, and that is what most production cutters do resulting in gems that are not as beautiful.

The Symmetry

As a cutter evaluates a piece of rough, they often will orient the gem so that it will yield the maximum weight as well as the best color. In doing so they sometimes will cut gems that are not quite symmetrical. For example, if they are cutting an oval and there is a distracting inclusion on the edge, they might choose to cut the gem so that it is slightly asymmetrical. This might be done in order to increase the gems clarity.

The gem on the left displays good symmetry.

Also, if there is an important color band that is close to the culet, and cutting a perfectly symmetrical gem might remove the color, thus diminishing its value, they may purposely cut the gem with the culet off center in order to allow that color to be reflected throughout the gem.

Sapphire Shapes That Are Most Valuable

When a cutter prepares to facet a sapphire, they have a lot to consider; they think about all of the factors but above all, they think about how valuable that piece of rough was and what is the maximum size that they can get and still have it sparkle. Did you ever wonder why diamonds are almost always cut in a round shape, but sapphires are seldom cut in rounds?

The natural shape of a diamond encourages cutting the round brilliant shape.

The natural shape of a diamond crystal encourages cutting the round brilliant shape. (see above)

The long, hexagonal shape of a sapphire crystal encourages the cutting of an oval or rectangular cushion. (see above and right)

Natural, pink sapphire crystal. See the hexagonal symmetry.

This rectangular cushion cut would maximize the yield from the rough.

Fine Pear shaped Sapphire

A pear shape sapphire may also offer a higher yield, based on the shape of the rough.

 

 

 

 

 

 

 

 

In the case of a diamond, as you can see in the image above and to the left, the rough crystals are cubic in nature and that means that in a perfect world a piece of rough could yield two perfect round brilliant gems. This gives a maximum yield from the rough.

What about sapphire? As you can see in the case of the three sapphires, above center and to the right, the natural crystal shape is a long hexagonal one. This means that the most efficient, weight saving shapes would be an oval, a pear or a rectangular cushion.

So what are the most valuable shapes in a sapphire? In my experience buying in the field, round and square cushion sapphires command a premium price. This is due to the fact that in order to achieve these shapes, you might need to sacrifice more of the rough material.

Carat Weight

The final consideration in selecting a sapphire is its carat weight.
Obviously there are only three ways that price can go as size increases. The price per carat will either go up evenly, it might go up exponentially or it might decrease.

In the case of very common gems that are readily available in larger sizes, the per carat price will go up evenly or even decrease. A decreasing price per carat might be due to the impracticability of using such large sizes in jewelry. Examples might be, quartz, kunzite and paler aquamarine.

At the same time, all things being equal regarding to color and and clarity, rare and more valuable gems such as ruby, sapphire, alexandrite and emerald will go up exponentially in value as the sizes increase.

Below is an example of blue sapphire and how the price might increase as size goes up.

Graduating price increase with blue sapphire

As you can see, there are many factors to consider in selecting and evaluating blue sapphire. In fact we only scratched the surface. For more interesting and relevant information about sapphire, check out this link to GIA (Gemological Institute of America), or here is also a link to the gem knowledge section of our website.

One of the biggest subjects that will have to wait for another day, are gem treatments and how they affect the value of sapphires.

My encouragement to you for now is to keep educating yourself. You can do what I have done for years. Study and learn several useful facts and then include them in your presentation right away. Remember though, facts and features are useless unless you are able to explain their direct benefits to your clients.

So take this information, apply it right away and have fun my friends. I hope to see you soon.

David Artinian