91% depth !?

[Rad_Fan]

I spotted a blue sapphire with this depth and somewhat decent crown height and table. It seems to preform normally and doesn't look dull/dead. I am puzzled as why the depth hasn't made the face up spread much smaller than others in similar carat weight. 91% is by far the biggest # I've seen.

Besides paying for the weight where I cannot see, what else should I be considering? Just wanted to hear your expert advice. Colored gems are so interesting and they make learning about them exciting!

 

[demantoidz]

Curious to read answers to your question. I have not noticed a deep stone that didn't face up smaller than shallower stones of the same weight so that is interesting (nor have I looked).

I came across a 90.4% depth intense pink diamond, weighing exactly 1ct, picture attached

 

[voce]

Face up area. But color most of all.

I've got an unheated blue sapphire that's 89% depth. This is to bring out the best color. I mean, generally the "ideal" depth for color can run anywhere between 60%-80%, so 80% to 91% depth can be relatively small in the grand scheme of things.

I suspect that some gems cut for color are less saturated in color per volume and also less dense. The more trace elements are embedded into the crystal structure that affect color and are heavier, the higher the density of the stone. So I can see why a stone less saturated in the crystal color is also less dense, and cut more deeply without losing face up size compared to a crystal that is more dense and saturated in color and cut less deeply.

 

[AV_]

The deep sapphires can be very beautiful, glittery & the bulk of material crtainly deepens colour. [same as for the pink, I think @demantoids - the crown seems very little so not too suprising the spread is not extremely small, or so I think] I remember seeing a few sapphires with depth greater than the diameter, the shape of a 'dog tooth' crystal quite aparent. Turn them bottom-up and you have a lightly faceted tall sugarloaf which dissapears into the setting.

Obviously, the setting needs to accomdate such proportions one way or another.

Digressing: there do exist modern cut models with such proportions, half-way to a briolette.

 

[lmyracle]

Is there a calculator to determine depth? Help me out with 8th grade math.