HomeDiamondsDiamond Re-cutting Diamonds and Colored Stones

 

As professional, grading and valuing gemstones, you will occasionally come across stones that need recutting and you need to know when it is worthwhile. Showing your customer how a stone’s appearance can be improved, what it will cost and how the value changes, will bring you increased respect. This often leads to a new setting and possibly side stones.

 

Old Diamond Cuts

What is color zoning?

Some stones show colors only in parts or layers. To describe the strength of this common but generally unwanted effect, we use four levels:-

1.      None: The color is equally distributed
2.      Faint: One might see changes in color saturation
3.      Gradual: The color weakens in some parts but not abruptly.
4.      Visible: Stone has clear color patches or layers.

Other than clarity, which is judged with a 10x lens, color-zoning is described only as far as it is visible to the unaided eye.

What is clarity?

The clarity of a stone is commonly described as being from "Free of Inclusions" over "Lightly", "Moderately", "Heavily" to "Excessively Included".

Here is how we describe a stones clarity:

- Free of inclusions: Even under 10x magnification no inclusions become visible
- Very Lightly Included: Only a pro with a lens might find an inclusion, but maybe not.
- Lightly Included: Inclusions are visible under a 10x magnification but rarely with the unaided eye
- Moderately Included: One might see inclusions with the naked eye, but they should not dominate the stone
- Heavily Included: Inclusions are clearly visible and influence the stone's appearance
- Excessively Included: A stone might not be durable.

4.24 ct Sapphire          3.87 ct Sapphire

Photo: Two "Heavily Included" sapphires with "Visible" color zoning. Remark on photo: While the yellow is too unevenly included, the blue has some "character", strong color but little luster, and it is not unattractive, though its value will be somewhere around only 5-10% of a similarly colored stone which is "Free of Inclusions".

What is brilliancy?

The estimated maximum of light which a stone reflects in one position under normal light conditions, High brilliancy is, amongst others, the result of skilled cutting.

What is depth?

It is the height of a stone divided by its minimum width. The "ideal" range lies between 60% and 80%. It is mainly determined by the given shape of the rough stone. Under 50% a stone might be called shallow. A shallow stone with a light tone will find it difficult to maintain saturation. A stone with 90% depth and a dark tone on the other hand might blackout.

What is cutting grade?

Brilliancy and depth are joined in the "Cutting Grade" which also includes the general quality and precision of the lapidary y's work and the finish of the stone. Here we will also mention any flaws or other weaknesses regarding the cut.   

All quality parameters are then summarized into an overall grade:

What is "overall grade"?

If you want to keep things simple you just have to look at theoverall grade which is described by five levels:

Excellent: Far above average and flawless. This quality is rarely seen in jewelry and is mostly acquired by collectors or long term investors.

Very Good: Above average in all criteria with one or two minor flaws.

Good: Average quality with strengths and weaknesses

Fair: Average quality with one or two obvious flaws

Poor: Major imperfections

900 of 1000 stones coming out of an average Sri Lankan mine will fall into the category "poor" and "fair", while only one(!) might receive an "excellent".

Stay tuned to geohavens for looking lovely diamonds, rubies, sapphires, pearls, jade and latest updates.  

 

Who are we?

The Geohavens name is an assurance of timeless beauty, distinct quality and uncompromising value. The Company spares no effort in sourcing from the farthest markets and the deepest mines in order to unearth the most attractive gems.

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