Bringing a Merelani Mint to life

[Roger Dery]

Hi all,
I'm not normally inclined to post unfinished photos of my work. But at the urging of several on this board, and with permission of the moderator, the following collection of photos is a layout of the process of working on a rough gem and taking it to completion. I realize this has probably been done before, but due to the unique character of this piece I felt there may be value in sharing the process here.

This particular piece starts out as a 25.40ct pastel green Grossular Garnet from the Merelani mining site in Tanzania; not far from where Tanzanite is routinely mined. As to where this piece started out, the most recent major pocket or collection of larger minty-colored Garnet was mined in mid-December of 2010. It was then sold and distributed over the coming weeks to several international buyers. I arrived just a couple of weeks later in early January - hoping to capitalize on the moment. While I did come away with several significant pieces which have all since sold, I had to travel to Bangkok a few weeks ago to negotiate for this particular beauty. And yes, the effort was worth it. As you will see in coming photos, it finished out to a nice size and has already shipped to a new home. So here goes....

Weight started out at just over 5-grams.


As you can see above on a very light colored background, it does not look really promising. In the hand though, it is something to behold.


As a general rule, I do not normally use my lapidary machine for preforming of the rough stones. But, in this case, as the rough was quite expensive, I did not want to pass up a more secure way to form the final shape - without wasting any more than is necessary of the host rough.


Getting a view as the outline is coming together. Notice the soapy effect to the water on the gloves - I suspect other lapidaries may put a little soap into their water sources as well as it make the final clean up a little easier.


A little closer to the final shape. Not stated earlier, but it will end up as a classic square antique cushion.


And now a little further re-shaping of the rough.


Nearly finished with preforming, and now making decisions as to final shaping. We're talking here about removing very small amounts to get the side alignments just a little closer. As in several tenths' of a millimetre.


Preforming is finished, and taking a moment to clean off any residue from the roughing process. It is imperative to have the rough stone as clean as possible before dopping as we want to develop the strongest bond possible.


Finished out with a pleasing shape and outline. And is now ready to be attached to a dop-stick.
*almost looks like a piece of candy!

Have to break for a spell to complete a project today, but will come back later with follow up photos of the faceting and polishing process. I hope you find this interesting, and maybe a little enchanting as the whole process can take a fair bit of time.

 

[chrono]

Looks like a gummy candy at the moment, which I'm sure many wouldn't mind as well. Thanks for posting the process and probably slowing your work on other stones too. My thanks to the mods in allowing these pictures and thread because it is very interesting and informative, giving us consumers a better appreciation for what lapidaries do in transforming what Mother Nature gave into beautiful sparking gems.

 

[pregcurious]

Thanks for posting this. Many of us will never even see such a gem in person.

 

[elizaloo]

Fascinating. I've just started buying small colored stones for future projects and to see one as it looks from beginning to end is incredible. Thanks for posting this process.

 

[pinkjewel]

Hi Roger- good to see you posting!!

Can't wait to see the whole process and the final gem!!

 

[JewelFreak]

Thanks for putting this up, Roger -- it's great to see the process. It's beautiful even before final cutting -- practically glows with yummy color. Thanks also to the mods for letting us see. Too bad it's already gone; hard stone to resist.

One of the great attractions of colored stones, to me, is the combination of human skill & artistry and nature. Appreciate your efforts to highlight that.

--- Laurie

 

[eastjavaman]

Looks easy, it only took me 1 minute to scroll from top to bottom.

 

[katharath]

Wonderful post/pics, you have my appreciation as well. This is one of my top five favorite gems so I'm excited to see this thread!

 

[royalstarrynight]

Great post Roger.

Thanks for taking the time to post! Looks like a green gummy candy now. I look forward to future posts.

 

[pandabee]

This is so neat Roger! Thank you for giving a little insight to the behind the scenes.

 

[Roger Dery]

Projects finished for today. And now some follow up regarding the Merelani Mint Garnet.

Shown below are some of the common tools used in the dopping of the rough (or a cut stone) to a dop stick. Typical alcohol style lamp that has been in use in the industry for 50 or 60 years, maybe longer. A stick of black wax used as the adhesive. This brand of black wax is referred to as "Banker's No 6". As it is also used in the banking, customs and export industries - places where one needs to apply a recognizable seal.

*sidebar: I use 4 different types of wax, and they serve various purposes. Some are more durable, or more or less sticky, some handle heat better and some not well at all.


Since I've already decided on the antique-style square cushion as the design type, now I am sizing up the rough to a 'cone' shaped brass dop-stick. I'm not actually attaching the rough to this dop, I am only using it as a crutch in the final positioning of the rough so that I can have it end at or very near the center-point of where I would like it to land (once attached).

*sidebar: I also use other types of adhesives such as epoxy or super-glues, but for most of my work the old-fashioned wax method suites me well. It also allows me to have the luxury of being able to soften the wax ever-so-slightly to move the centerpoint of the rough to meet or match up with the centerpoint of the dop - if or when needed.


The aluminum fixture below is no longer manufactured, but is a typical tool or fixture used to assist with attaching the dop to the wax and to the gem rough. The brass dops are allowed to slide back and forth within the VEE groove in the metal fixture. Assuming they are aligned well to each other, it makes for a good fit of all the individual components. The gem rough is placed in-between the dops and then the dops are tightened in place.

At this point, one would warm up the brass dops gradually (being careful to not overheat the rough) and then apply the wax to both parts (metal and rough). Hopefully one acquires a nice solid adhesion joint.

If the gem rough is already preformed, and appropriate dops are available, and after much practice, it is possible with multiple dopping fixtures to form a production line and complete 25 to 30 dopped joints in an hour. This is assuming speed was a necessity, and enough equipment was on hand, available, and clean. Given that speed is not always the most important factor especially with pricey rough, I find myself spending between 2-4 minutes to complete the dopping process with wax. *caveat - it always seems to take longer with very delicate or heat sensitive roughs such as Apatite, Mexican Fire Opal, Kunzite, and even Peridot.

Hope you all are finding this interesting. More to come later or tomorrow.

 

[Roger Dery]

Now we are actually working on the gem, and placing specific facets around it in a particular fashion. When I was pre-forming the rough earlier by hand I used a 600-grit-size lapidary wheel. 600 grit particles equate to roughly 30 microns in size. When I began applying individual facets as shown below, I was using a 1200-grit size - which translates to roughly 15 microns.

The concept is, that as we continue to reduce particle size, the finish improves until we reach an actual "polished state". This is when the micron size being used falls below 1/2 micron - which of course is unbelievably tiny. Other options exist to create a polished state such as using one of the oxide type polishes, but for this exercise we are continuing with a diamond grit polish.



In this magnified photo you can see the individual defined facets, and they have a frosted appearance. This is a result of the 1200 diamond grit particle size. You are viewing 8 individual pavilion facets meeting at a common junction that we know as a culet.


This design incorporates 3 individual step-style tiers, spread over 4 quadrants on each of the 4 sides of the gem's outline. And, actually, there is a small 5th section to the sides, but it is only visible at the girdle line and somewhat hidden after the first tier below the girdle. Of course, the prize goes to the person that locates it.... just kidding!

....more to come tomorrow

 

[MakingTheGrade]

Mmmm..candy!

 

[Roger Dery]

Having completed placing the desired number of facets, we work towards completing a pre-polished state on the surface of the gem. In this photo the arrow is pointing to a section of facets that are still exhibiting the frosted appearance of contact with a 1200-grit surface.

*sidebar; the 1200 lap used is where the 1200 grit particles are "sintered" into the surface. It can not be renewed or refreshed as in adding in additional grit particles. This type of lap is durable and long-lasting. There are also other types of 1200 grit laps but generally speaking they produce a similar surface finish.

The facets on either side of the 1200 surface have been pre-polished with an 8,000 grit embedded surface on a Zinc lap. 8,000 grit translates into 3 micron particle size. The Zinc lap has the capacity to be "re-charged" over and over again. After performing pre-polish on several gems, the surface can be "reloaded" with additional loose diamond grit. The Zinc type of lap is best suited for being used as a pre-polish lap in either 3,000 (6-7 micron), 8,000 (3 micron) or 14,000 (1 micron) grit sizes. In addition, there are other types of laps that can be used for pre-polishing.


At this point each pavilion facet has been worked on by the 8,000 grit Zinc lap and the pre-polish is complete.


Now that the pre-polish is finished, then each facet is touched again in the exact same individual locations by the final polish lap - which in this case was with a 100,000 diamond grit size (.25 micron in size). The type of lap used on this gem for final polish is known in the trade as a Matrix™ lap and is ideally suited for a very fine polish at 50k (.5 micron) or smaller diamond grit.

Due to the value of this Merelani Mint I felt it important to polish the girdle as well.

still more to come....

 

[NexivRed]

This is fascinating... keep going! It really adds to my appreciation of a well cut gem. The work involved is incredible.

 

[Roger Dery]

With pavilion complete, the dop/gem combination can now be installed in the aluminum transfer fixture. Another dop, of the appropriate size, has been inserted in the opposing VEE section to meet the incoming cone of the finished pavilion. As one can imagine, it is helpful if the axis on one side matches the axis of the other.


On the original (completed) side black wax was used for adhesion. To assist in facilitating a safe transfer, I've used a wax that has a lower melting temperature. You will notice the wear on the brass surface as these dop sticks are re-used over and over.


Transfer complete, wax is now removed from the completed side. And then of course it is time for inspection to ensure everything has taken place as planned.

 

[Roger Dery]

Transfer now complete, working through the developed facet plan for the crown. At first glance, it may appear that we have a very small table. However, what has happened here is that we simply "ran out of room".


I've taken the liberty of using a brass tracing pencil and rubbed it over the outline to accentuate the relationship of one facet to another. The facet arrangement is such that there are two 'main' facets per side. They are larger than the other facets. In addition, there exists a 'false-girdle' line above the actual girdle. This is designed to elongate the path of light as it transfers through the gem causing a slight increase in color saturation.

And now, the table is in place. It makes up roughly 60% of the width of the stone. The facet was installed using the 1200 diamond disc mentioned earlier.

Then, what you see here is a very nice pre-polish effect. This was done with the 8,000 diamond embedded Zinc lap.
- so far, so good!

Not much more to go....

 

[Trill]

Fascinating thread! Thank you Roger for taking the time to post this, and thanks to the mod for allowing him. It really adds to my appreciation of the skill and artistry involved in precision cutting.

 

[T L]

Transfer now complete, working through the developed facet plan for the crown. At first glance, it may appear that we have a very small table. However, what has happened here is that we simply "ran out of room".

How would it have looked with the small table left intact? I actually prefer small tables like that on gemstones, I wish more lapidaries would do them.

 

[Roger Dery]

Even though the condition of the crown facets appear complete, they are only at the 8,000 grit size (3 micron). For custom faceters this is a pre-polish condition. In some developing nations where the equipment is either not yet advanced, or they don't care to advance, this type of finish may be considered a completed product. It would not be uncommon for some custom faceters in north America, Europe, Australia or even South Africa to pick up these (presumed finished) gems, give them a proper top-notch finish and then offer them to clients.
*I'm not suggesting this is good or bad, I am only sharing that the concept happens.


Getting closer to a final finish. At this point - though may be hard to believe - this is a well-executed 8,000 pre-polish finish on a Zinc lap. It will be completed using 100,000 grit particle size diamond on a ceramic-style compound lap known as a Matrix™.


The polish is complete, and is time to remove the Garnet from the dopstick.

A little more to come....

 

[Roger Dery]

Transfer now complete, working through the developed facet plan for the crown. At first glance, it may appear that we have a very small table. However, what has happened here is that we simply "ran out of room".

How would it have looked with the small table left intact? I actually prefer small tables like that on gemstones, I wish more lapidaries would do them.

Hi TL,
I'm sure it would still look nice. For me, I too prefer a higher crown and a smaller table. It is an appearance that appeals to me.

That being stated, I do not buy my own gems. The vast majority of my goods go to designers, custom jewelers and regular jewelry stores. And, unfortunately, there is a sense of conformity in this type of sales venue. In that, generally speaking, their buyers have a low appreciation of unusual or non-standard design elements - like high crowns and small tables - or non-standard outlines.

However, when we perform sales events around the country, that is when the outside-the-box-thinking gems sell quickly, thankfully.

 

[Roger Dery]

Looking very good here.... final polish completed.


Here's how the final facet arrangement lays out. Keeping in mind, this was a work-in-progress. As the final outcome of the facets was decided 'on-the-fly' as I was working on the stone.


Looking through the bottom.


Looking into the top.


Final stats
Starting weight: 25.40ct (5.08grams)
Finished weight: 10.84ct (yielding a return of just over 42%)
Dimensions: 12.3 x 12.3 x 9.25mm
*yes, a fair bit of lint on the gem! I'll see if I have a shot sans lint.
**in the hand, I believe it is ever so slightly lighter in tone.
It has been sent off for professional photography before being delivered.

 

[chrono]

High crown + small table = helps preserve more of the original material too. Such a pity you had to grind away so much from the top.

 

[T L]

The outcome is very pretty, but in future, I would have tried to keep the original crown work. I have a stone with such a crown, with a tiny table, and it has a beautiful antique looking charm, not to mention it retains so much sparkle that people often think it's a garnet (it's a tourmaline). Nice job, and thanks for sharing all your work, very much appreciated and very beautiful stone.

 

[minousbijoux]

Roger:

Bravo, just Bravo!!! It is threads like this that imo, make PS a well regarded and unique place. I don't know where to begin in thanking you for the photo documentary (I know there is an actual word for this, but it escapes me). The quality of the photographs is outstanding (thanks Ginger, I presume), and the teaching/knowledge is excellent.

I have a few questions but for now I'll ask a follow up question to TL and Chrono's discussion of keeping a high crown and tiny table. Let's just say you had done that, and kept it intact as TL suggested. What would that have done to the emission of reflecting light? Would it have dramatically changed the appearance of the stone (either making it appear more saturated in color or darker), or do you have that much leeway in faceting without disrupting the light refraction?

 

[T L]

Transfer now complete, working through the developed facet plan for the crown. At first glance, it may appear that we have a very small table. However, what has happened here is that we simply "ran out of room".

How would it have looked with the small table left intact? I actually prefer small tables like that on gemstones, I wish more lapidaries would do them.

Hi TL,
I'm sure it would still look nice. For me, I too prefer a higher crown and a smaller table. It is an appearance that appeals to me.

That being stated, I do not buy my own gems. The vast majority of my goods go to designers, custom jewelers and regular jewelry stores. And, unfortunately, there is a sense of conformity in this type of sales venue. In that, generally speaking, their buyers have a low appreciation of unusual or non-standard design elements - like high crowns and small tables - or non-standard outlines.

However, when we perform sales events around the country, that is when the outside-the-box-thinking gems sell quickly, thankfully.

For some reason, I didn't see this post until after I posted a second time. Thanks for explaining. It makes sense to appeal to your customer base.

 

[Roger Dery]

Roger:
I have a few questions but for now I'll ask a follow up question to TL and Chrono's discussion of keeping a high crown and tiny table. Let's just say you had done that, and kept it intact as TL suggested. What would that have done to the emission of reflecting light? Would it have dramatically changed the appearance of the stone (either making it appear more saturated in color or darker), or do you have that much leeway in faceting without disrupting the light refraction?

Hi Minou,

Many domestic gem cutters have moved over the past 25-30 years to using published designs that they either purchased or acquired from other sources, or they developed the Cad skills to create their own. And, many of them are quite proficient in Cad.

Using Cad programs, it is possible to adjust the angles in software and not have to be concerned with final output because it is performed for you. [that is, not the actual faceting of the gem, but the placement/movement of angles on a computer screen]

Many of your professional (or commercial) cutters may use Cad as a help, but it is not the "be all, end all" answer to creating a beautiful gemstone. If I only worked on man-made rough materials that were nearly perfect with ideal hue, ideal saturation, and ideal tone, or were so lucky to ONLY buy perfectly clean gem rough with the same color characteristics, then I could take vast liberties with how a gem came to completion.

But the reality is I have to work with the types of gem rough that become available in world marketplaces. In the example of Merelani Mint Garnets, there is very little clean gemmy rough available, especially in larger sizes.

So, when it comes to design elements such as small tables and high crowns, I have to take all the variables into account and meld them together into a sale-able gemstone. For the particular Garnet shown above, making the crown even higher and incorporating a much smaller table would have increased the depth of color some - maybe enough to move it out of a Merelani Mint category and into a Tsavorite. To the client, I had promised a Merelani Mint of significant size. I hope I've met their criteria.

 

[Laila619]

Really cool! Thanks for sharing this fascinating process!

 

[JaneSmith]

Gorgeous stone, fascinating thread. Thank you so much for this, I really appreciate it.






I kinda need a green garnet now.

 

[The sun is shining]

Wow. What a stunner. Thanks for sharing, Roger!