Face Up Size

[pwsg07]

I got a pink sapphire. It is 1.09 carats and the dimension is 5.7 x 3.9 mm.



vendor's photo


The colour is quite close. The stone IRL is more vivid in colour. There are some nicks/abbrasions on the joint of the crown facets which don't show on the photo.

I was shock by the small face up size of the stone. Before I have seen this stone, I concern only the weight, not the face up size.

What is your desirable face up size?

Thank you.

 

[Stone Hunter]

It depends on what I want to use the stone for. Colored stones are often cut deeper than diamonds and so more of the weight is in the depth of the stone.

Because the color is intense you can put a small stone in a ring and have it look good. Depending on your finger size of course. If you have a larger finger size then the setting can take up more of your finger if you feel the need for finger coverage.

Here is a 5 mm x 7 mm lavender sapphire set north south on a size 5.5 finger. It's a small stone but because of the color it stands out.

 

[chatoyancy]

Pwsg07 and Stone Hunter, your sapphires are so beautiful! Sapphires have a high sg, so they are going to face up small anyway. Pesg07, the intense pink color packs a punch though! Gems always look so much bigger to me once they are set. What are your plans?

Most of my stones arrive looking about the size I thought they’d be, but cut and sg really can make stones face up smaller or bigger than you think. I was surprised at how tiny my pear shaped spessartite looked. It’s 1.06 carats. I was surprised at how small by gray sparkly bel was considering how close to a carat it was. I totally went for color and cut (cushion). It’s .96 carats, I think. My biggest surprise though was how huge my 2.49 carat oval amethyst looked when I opened it. I swear it looks like over 3 carats.

 

[pwsg07]

Thanks Stone Hunter and chatoyancy.

I have no plan for this stone yet. I just bought it because I have no sapphire. This stone has a small window that doesn't show on the vendor's photo.

I have a 3 carat blue tourmaline. It looks larger than my other 3 carat stones.

 

[Michael_E]

I have a 3 carat blue tourmaline. It looks larger than my other 3 carat stones.

Tourmaline is not as dense as some other stones, so it's going to be bigger at a given weight than they are. Sapphire is different as it's more dense than say, diamond, so will generally have a smaller face up size than diamond or other stones, for a given weight.

 

[Bron357]

Yes, they always look bigger in the photos!
Yes, sapphires have a high specific gravity and carat is a weight not a size. So you get a smaller looking gem for the carat weight.
For a “good size” on a finger (in a ring) I think you need sapphire of 2 carats plus.

 

[Frost]

Everything everyone already said above, plus another thing on top to explain why they're cut deeper: saving weight.

The natural crystal shape of sapphire, and the usual forms in which its found (alluvial pebbles or broken crystals) is not especially suited to gem cutting.

The high quality rough is prohibitively expensive literally from the mine onwards and on top of that, even the best cutters cannot estimate how the color and the clarity will turn out with 100% certainty. So in other words, you pay a lot for something that's risky and may or may not turn out the way you'd like it to. And since prices start at the mines, most dealers choose to save whatever weight they can in order to maximize yield (and in some cases, protect color zones and ensure the stones keep their colors).

The entire 'native cut' idea is really a reflection on the way the gem market works (rather than, as often assumed, the skill of the cutters). It's entirely possible to get precision cut gems in source countries... If one is okay with the result being a small stone with a high price per carat.

All that said, I'd take a reasonable or actually good cut - with focus on beauty, where it should be - over potato-cut gems anyday.

 

[doberman]

Remember that corundum (sapphire) is denser than diamond. So it will face up smaller by weight. Beautiful pink sapphire!

 

[digdeep]

Do you have a caliper? They are cheap and usually vendors give you the size of the cut gem (5 x 7 oval, 6.5 mm round, etc......measure it on your caliper and you'll have a visual display of the face up size of the gem! Easy Peasy.............

 

[PrecisionGem]

One thing often over looked is the girdle thickness. I see many cutters leave a very thick girdle, especially newer cutters. It's just so tempting to do when you have enough stone left while cutting the crown.
There are a few downsides to this, mostly for the customer, and one upside.

1. Jewelers hate working with really thick girdles.
2. You are paying for this extra weight, that has no benefit.
3. Optical performance is often adversely effected. (I'll show this later on)

The one plus is, if you are really hard on your stones, and bang up the crown, there is enough material left to recut it.

As an example, I took one of my popular round designs, and in a 7 mm cut, a proper girdle thickness produces a stone of 1.51 ct.

An overly thick one will result in a stone of 1.97 ct. Now if the stone was say $500 per ct. this means you are paying an extra $230 for this thick girdle!

 

[Stone Hunter]

@pwsg07 I think the pink looks very good for a stone you have no plans for. Congrats!

@PrecisionGem That's interesting! Thanks for sharing your perspective. I wouldn't know how to tell if the girdle on a stone I'm considering is too thick. That's not something I've seen listed for colored stones.

 

[PrecisionGem]

A good range for thickness is 0.5 to 1.2 mm.

 

[Cockatiel]

One thing often over looked is the girdle thickness. I see many cutters leave a very thick girdle, especially newer cutters. It's just so tempting to do when you have enough stone left while cutting the crown.
There are a few downsides to this, mostly for the customer, and one upside.

1. Jewelers hate working with really thick girdles.
2. You are paying for this extra weight, that has no benefit.
3. Optical performance is often adversely effected. (I'll show this later on)

The one plus is, if you are really hard on your stones, and bang up the crown, there is enough material left to recut it.

As an example, I took one of my popular round designs, and in a 7 mm cut, a proper girdle thickness produces a stone of 1.51 ct.

An overly thick one will result in a stone of 1.97 ct. Now if the stone was say $500 per ct. this means you are paying an extra $230 for this thick girdle!

Hi Gene,

I actually have the opposite problem with one of my stones. A loose spinel I have is was sold as 2.00 carats, and it has a very thin girdle. I am guessing it was left like that so it stays at 2.00 carats and faces up bigger. However, it's the thinnest girdle I have seen and it feels very sharp to my finger. It is actually chipped, or shattered, rather, in one area, and I was thinking about recutting/repairing the stone to fix the issue. The rest of the stone is OK. In repairing something like that - generally speaking - would it be feasible to cut around the periphery of the stone to make the girdle more normal thickness? Or is that too simplistic, and a more drastic recut would be indicated.

 

[T L]

One thing often over looked is the girdle thickness. I see many cutters leave a very thick girdle, especially newer cutters. It's just so tempting to do when you have enough stone left while cutting the crown.
There are a few downsides to this, mostly for the customer, and one upside.

1. Jewelers hate working with really thick girdles.
2. You are paying for this extra weight, that has no benefit.
3. Optical performance is often adversely effected. (I'll show this later on)

The one plus is, if you are really hard on your stones, and bang up the crown, there is enough material left to recut it.

As an example, I took one of my popular round designs, and in a 7 mm cut, a proper girdle thickness produces a stone of 1.51 ct.

An overly thick one will result in a stone of 1.97 ct. Now if the stone was say $500 per ct. this means you are paying an extra $230 for this thick girdle!

This girdle thickness issue can mean thousands of dollars when it comes to diamonds too!