courses for rough coloured stones

[koester_2010]

Hello,

can everyone tell me, where I can make a course for rough coloured gemstones ? It seems to be very difficult.

Mathias

 

[chrono]

I don''t quite understand your question. Are you asking about courses to learn to identify gemstones in the rough form? Courses on buying rough for faceting?

 

[Roger Dery]

Mathias,
You asked: "can everyone tell me, where I can make a course for rough coloured gemstones ? It seems to be very difficult."

If you are asking whether there is a course available to learn about rough gem material for gem cutting.... to my knowledge this type of situation does not exist anywhere in the world. It is possible you could take a course in Mineralogy from a college or university, but it may not assist you with learning about rough gems, specifically. Gem cutters and lapidaries will generally learn hands-on from another cutter or mentor, or through a lapidary club, or immersing themselves into the rough buying marketplace. Of course, the latter will be the most costly, but the quickest way to absorb the knowledge.

I hope you find this helpful.

 

[FinewaterGems]

Hi Roger,

Glad to see you''ve joined the forum!

All of us cutters probably all have a small stash of rough that we''ve learned our lessons on. One of these days I should just donate it to the local faceting club for practice material - it''s kind of painful to look at it now!

Best Regards,
Gary

 

[chrono]

Roger,
Welcome to Pricescope and I am delighted you have joined us here. I have long admired your cutting and selection of gemstones.

 

[Roger Dery]

Hi Mathias,
Thought I would offer some very basic information so that when the time comes and you are placed in a position of having to make decisions on rough, that you would have a little info, as compared to none at all. There are some basic things one should look for in rough. This is, assuming, the rough dealer you are working with knows what he has and is sharing with you legitimate information and identifying each item or parcel correctly. If you are working in a developing nation, this may not be the case as many are not informed as to what they have. Your risk is lowered if acquiring the rough in the US or Canada.

Species - must be the type you are interested in. Your supplier should know what they have.

Size - is important as it must match up well with your desired outcome. Though, when cutting free-sizes as custom faceters do, this is less important.

Color - as in hue, tone and saturation; but for this purpose, the color ''should'' be close to the final desired color, but it usually comes out darker (though there are a several exceptions). There is a technique known as the ''white-paper-test'' that is commonly used by gem cutters to determine a relative final color after cutting. I can state without any doubt that it is not fool-proof, but it is helpful. If necessary, I will share the technique at another time (it''s wordy).

Clarity - clarity could never be as important in colored gemstones as what is found with Diamonds. But it is always nice to have clean goods to facet. However, the nature of most colored stones are that they are generally not clean like Diamonds. So one must learn how to live with them, or work around them. Either way it is lengthy learning curve to work through. After 28 years I am still learning new things about clarity, and so will you.

Enhancement (if any) - some colors (in some species) are only available after some form of treatment. This must be disclosed, and especially so if the enhancement is not permanent. Some trade associations and government entities have further info and requirements in this regard. But it is good practice anyway.

Shape and/or crystal habit - it is helpful if the natural outlines are conducive to produce your desired outcome for shape. An example would be where you may find elongated intact crystals. It would be wasteful to cut rounds because the yield may end up in 10 to 15% range, where if it was cut in one single stone the outcome may be over 40% yield.

Here is an example of Tanzanian golden Scapolite rough. This piece weighs over 13 grams (65 carats). From the end of the crystal, it appears to have a ''boxy'' outline, but it is an elongated crystal that would comfortably produce at least two nice sized gems, or maybe three smaller. This particular piece of rough has a very ''glassy'' like appearance, and gererally this is desireable. Not every species exhibits this characteristic so it is prized by many faceters. In a follow up I will show the first stone cut from this crystal.

 

[Roger Dery]

Mathias,
The Scapolite crystal from the previous post was elongated. I used my trim saw and cut it in half so that it easily produce two stones. Here''s one of them completed in one of my original designs. Scapolite is not well-known in the jewelry community as it is mostly a collector gem. The picture below is a little over-exposed and so it does not really represent this stone well. It is a little richer in the hand.

I hope this has been a little helpful to you.

 

[chrono]

Roger,
Thank you for the information and picture of the end result. It is very good reading material. I would love to read more about it even though it might get wordy.

 

[icekid]

Date: 5/24/2009 4:15:39 PM
Author: Chrono
Roger,

Thank you for the information and picture of the end result. It is very good reading material. I would love to read more about it even though it might get wordy.

Ditto! We are going to love having you around, Roger

 

[T L]

Don't forget about dichroism Roger. For example, if you were to cut that scapolite's table along one axis, it might be a dull color, and along the other axis, it might be a brighter yellow. I think that's also part in parcel of what faceters really need to look at. I've seen so many cut them along the wrong axis, and they may have more carat weight, but they sacrafice beauty instead. Tourmalines are typical of this faulty cutting for weight vs beauty.

 

[chrono]

I wonder what''s the trade off in pricing? Maybe the larger side with less intense colour might sell for more than cutting along the axis with the bright colour (but smaller end result) because the weight loss is just too much?