Sphalerite Project

Hi guys,

I have to say that I am a bit confused about the recent posts requesting being "signed up" to my list. Since the posts came here, those persons already ARE signed up! LOL! Did I miss something?

Well, anyway - down and out again so have some keyboard time. Got hit in the chest with a 6 foot long 26 pound ground bar, and banged up my ribs pretty good - x-rays say that there are no breaks, but I beg to differ - despite that, I am somewhat incapacitated for a bit, so have to do easy things like type. :-)

So, how have things been? Anyone working on anything special? Drop us a note and let us know. I have a project going right now which is a recut of a sphalerite for a friend back east - it was natively horribly cut and scratched all the heck. Gonna fix that - of course a little help from our old friend Mr. BOG was used to set the project up. Also, I ran through the things that I told you all about before.

So, let's use my sphalerite as a training tool here real quick. Using the info I gave all of you for the peridot project (I will put up the diagram for that in a second), what would be the first step in cutting the gem? Let's assume that this is a near perfect spherical shaped rough (something that would never happen in nature but will make this easier), and that you are going to prepare to facet it.

What would be the first step?

Best wishes,
Paul

For me, the first step was to look up in VARGAS,s "Faceting for Amateurs" what the heck you were talking about. How large is the stome? Vargas said some pieces go as large as a pound!!!

bobe

--- In PaulAhlstedt@yahoogroups.com, "Paul" <ifapresident@y...> wrote:

> Hi guys,
> - - -
> So, let's use my sphalerite as a training tool here real quick. Using
> the info I gave all of you for the peridot project (I will put up the
> diagram for that in a second), what would be the first step in cutting
> the gem? Let's assume that this is a near perfect spherical shaped
> rough (something that would never happen in nature but will make this
> easier), and that you are going to prepare to facet it.
>
> What would be the first step?
>
> Best wishes,
>
> Paul

Deffinitely consider 3 things :

1. Sphalerite's extreme multiple cleavages! 6 or 12 I think!
2. Sphalerite's softness
3. Sphalerite's Color.

The cleavage I know from experience is a pest. As is the softness, but that's easy to come past, where as the cleavages are all over. Keep the design simple, and try to orient after the cleavages.

The color only affects how big your stone can get without closing off the light.

Jón Olaf Svane

<<<For me, the first step was to look up in VARGAS,s "Faceting for Amateurs" what the heck you were talking about. How large is the stome? Vargas said some pieces go as large as a pound!!! bobe>>>

Holy smokes, I sure would like to see a one pound facet grade sphalerite - that would be a trip to cut. :-)

Paul

<<<Deffinitely consider 3 things :

1: Sphalerite's extreme multiple cleavages! 6 or 12 I think!
2: Sphalerite's softness
3: Sphalerite's Color.

The cleavage I know from experience is a pest. As is the softness, but that's easy to com past, where as the cleavages are all over. Keep the design simple, and try to orient after the cleavages.

The color only affects how big your stone can get without closing off the light.

Jón Olaf Svane>>>

Excellent Jon - so what would be your first consideration in setting up this job? - let's say that the material is colorless and a perfect sphere just to eliminate those two issues. What would your thought process be at this point, and how would you continue?

Best wishes,

Paul

> 1: Sphalerite's extreme multiple cleavages! 6 or 12 I think!
> 2: Sphalerite's softness
> 3: Sphalerite's Color.

#4 - The rotten egg smell while grinding!

Marty

Ah!

A challenge?

I've tried to summarise some thoughts on

http://www.nojfalo.dk/facet/sphalerite/faceting sphalerite.htm

Funny you say colorless, sphere. That's no natural rough, but it might well bee synthetic. But it would show the extremly high dispersion very well.

Sincerely Jón Olaf Svane

It looks like Jon did a great job with his overview of faceting sphalerite. I did have just a bit of trouble getting to his web page until I saw the space in the file name and inserted %20 for the space character. The URL below should be clickable.

http://www.nojfalo.dk/facet/sphalerite/faceting%20sphalerite.htm

good work Jon. I have a big piece of sphalerite I need to cut and this is good review. What fantastic RI and display of dispersiion if your rough is clean and lightly colored.

Dan C

<<<It looks like Jon did a great job with his overview of faceting sphalerite.>>>

Boy, I'll say - great write-up Jon. I used to work in military optics manufacture, and of course synthetic sphalerite is used quite commonly so I cut a lot of the cutoff material. The smell is somewhat annoying, but the finished product is mind blowing - talk about some optical "jazz," syn. sphalerite has it.

A couple things off hand that need to be added. One is that you really shouldn't get sphalerite hot during any stage of faceting, primarily this means NO wax dopping. Go with epoxy or cyanoacrylate, but remember that epoxy will shrink 5% or more, so keep the bond line as thin (and small) as possible - if you do not, you will exert considerable mechanical stress on the gem and possibly cleave it.

However, this are just warning notes as I think that spalerite is a material like fluorite where the cleavage is not as bad as would be thought (or bad as it is reported in other sources) - and most of you know that fluorite is really not that much of a bummer in terms of cleavage - feldspar is another, etc., but I am just saying best to be careful rather than sorry.

The greatest bit of wizardry is in choosing the correct lap - you should use the finest lap that you can to get the job done - start with 600 as Jon points out, and get finer if you can. I have often just cut sphalerite with a 3,000 and then be done with it. Problem is, like the calcite Jon mentioned on his page, sphalerite will also give a sort of "suction" type of feel on the lap the finer the lap gets - and that will most often pull cleavage fragments out of the surface of the facet you are cutting if you are not careful.

For this reason, use light pressure, and using the mindset behind the models that Jon made, always try to cut in a direction which compresses the cleavage planes - use your motor reverse switch heavily here for that.

When you go to polish, use your favorite method with high lubricity, such as diamond or alox with extender fluid, light oil, etc, as this material will easily scratch and abrade with the slightest friction.
This is one gem I don't use my normal water & Linde slurry on, although you can if you are gentle with it (use a heavy slurry).

I recommend using the finest diamond that you can get away with, or you could even use alox powder b with a lubricant other than water and that would be fine as well - the issue here is that the more "glossy" you get the surface, the more that material kicks butt. :-)

Note however that the longer you stay on a sphalerite facet polishing it, the more it will round - so get it as fine as you can with your prepolish and then hit it as quickly as possible to bring a good polish up and then move on to the next facet. The best polishing laps are those that are gentle, I think Jon said he used a plastic, and something like a resin Pol-A-Gem, Corian, Ultra-lap (and more traditionally a wax) should all probably be good gentle laps to use for polishing. Also note that because of the softness, you can still OVERCUT while you are polishing - so pay careful attention to that to keep your meets.

A final note might be that sulfur and sulfur compounds are NOT good for your faceting machine, so be sure to clean up religiously after you are done. A gem of some 10mm in diameter or greater in a lighter body color is worth the trouble, and a great addition to a collection - as well as being a great learning tool.

Oh, and pay particular attention to Jon's warning - use SLOW lap speeds at all times. This IS NOT a material that can handle higher lap speeds. Incidentally, the one I am cutting is a beautiful bright yellow, and will absolutely blind you once it is cut - when you have a stone like this with a light open body color, go with a lot of facets as it will do some mind boggling scintillation (they need to be flat to work though, be careful of facet rounding).

In closing, I would like to thank Jon for the excellent work he did - and on behalf of all of us, keep the lap spinning dude!

Paul

Dan and Paul!

Thanks for the kind word, you've given me the nicest crimson look right now.

All I did was to take up the challenge, stop a litle and think what I really did, and write it down. By the way, that's an exercise one should do more often - in general.

Taken Dan's hint on my space in the Html-name, I've incorporated an FAQ-page in my faceting-pages on my site (www.nojfalo.dk) linking to Sphalerite (and Amber, which is the only other "How to" I've formalised).

If I may, I will incoporate Paul's recommendations on dopping, cutting and polishing Sphalerite. It would be great to se a picture of that yellow Canarie Bird, when it's finished.

Jón Olaf Svane

<<<If I may, I will incoporate Paul's recommendations on dopping, cutting and polishing Sphalerite.>>>

Hi Jon,

That's fine, I don't mind at all. Sphalerite is really a kewl gemstone - I just wish it was harder. :-) It would make some unbelievable jewelry, yes?

I guess the real or most challenging problem with sphalerite is really the scratching issue - that is where that gem will make a faceter out of you. It will often scratch, or get little tiny fragments break off a facet edge and skate across your work and.... well, you know what happens then.

I find that for me (and I have to qualify this statement with the fact that it is what works for me, I don't know how else to present this, so it is my opinion only) I have the best luck with lots of water on a Raytech NuBond in 3,000 mesh for all grinding. In essence, you do the grinding and prepolishing all with one grit. This has the advantage that the lap is so fine and gentle, it really greatly minimizes the tendency to scratch and so on.

My 3000 mesh NuBond imparts what I would say is about a 8000 mesh finish, so it is actually pretty near a polish to begin with - subsequent polishing is then fairly easy.

The one problem here is that you can only use this method on normal jewelry sized stones - if you have one of those 100 carat whoppers, you definately will have to default to the 600 for rough grinding.

I guess the overall trick here is to use light pressure, as fine of laps as possible for the application, and very slow lap speed with lots of water - and the polishing method should produce as little friction as possible.

Anyway, just my two cents, your milage may vary. :-)

Best wishes,
Paul