ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 18, 2008 2:49:09 GMT -5
Hello everyone,
I am new to this board and still pretty new to gem cutting and polishing. I have made several cabs that have turned out pretty nice, however I have not been able to get a star yet. I have bought several books on the topic and have somewhat gotten a star on my most recent piece, but I am having a problem getting the rays of the star to extend across the stone. It is a ruby from Kenya, and has polished very nice at about 15c. In the dead center of the top of the stone is a silvery triangle, and a six ray star is centered on that. When the stone is turned the star dances along the edges of the triangle, but won't extend down the rest of the stone. As of now I have about 14 hours into the stone, with approx 10 of them for just polishing. I used a 180 grit to shape, then 325, 600, 1200 grit polishing disks, as well as a final polish disk. I then used a 3000 grit Crystalpad, and I am now using a leather pad with 100,000 grit, 1/4 micron diamond abraisive alternated with a tech 10 pad with the standard polish that comes with it. The surface of the stone is almost a perfect mirror finish under 15x magnification. Sorry I don't have any pictures yet. Anybody got any ideas??? Thanks for your input.
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Post by larrywyland3 on Apr 18, 2008 6:03:25 GMT -5
I have not done any; yet. I bought some years ago that were already cabbed. I noticed that they have extremely high domes. They were almost like spheres that were cut in half. One person that I buy from stars rose quarts and his technique is to make a sphere and then look for the star and cut it in half to get two cabs. Hope this helps.
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 18, 2008 13:34:01 GMT -5
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adrian65
Cave Dweller 
Arch to golden memories and to great friends.
Member since February 2007
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Post by adrian65 on Apr 18, 2008 15:17:20 GMT -5
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ljhemmer
off to a rocking start
Member since April 2008
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Post by ljhemmer on Apr 18, 2008 17:28:53 GMT -5
The striations in the pictures appear to be inside the stone, could they be blocking the rays from extending ?
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 18, 2008 19:20:42 GMT -5
After continuing to polish.... (for hours) have gotten the legs of the star to extend further outside of the "shiny triangle" area.... but they are darker & blurry... not sharply defined. With a loupe the surface still appears pitted?? I don't know if I'm missing a step??
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 19, 2008 11:04:21 GMT -5
This seems to be the best that I can get it.   This next one is under white light to show the dome  |
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 19, 2008 11:05:52 GMT -5
BTW, since I didn't have anything in the pics for size reference.... it's 10.6 carats  |
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Post by Tony W on Apr 20, 2008 0:57:02 GMT -5
Great work on those! I have been practicing on mine run and getting stars but mine are just blobs of light the move around... you actually have stars. My material is pretty poor, with lots of inclusions that break up the light.. so my thinking is that the better the material, ie. clear, the better the star. I have read that it is also a practice with some cutters to put a dome of sorts on the bottom to accentuate the star, but I can't say for sure. Anyway, you've done well! It is one of my fondest hopes to one day star a sapphire I've found. T
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 20, 2008 12:04:46 GMT -5
Thanks Tony. I haven't had much luck with the rubies & sapphires that I got on a trip to North Carolina either... very frustrating!! So I tried some of the eBay sellers (mostly crap quality - worse than NC), but I did find one *gem* of a seller.
The above shown stone is a Kenya ruby from sandsational, you might want to check out his listings... great prices & good raw material to work with, also an excellent seller with great communication. Good luck!
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Post by stoner on Apr 20, 2008 22:25:04 GMT -5
I'm no expert on rubies, but it looks to me that this particular stone has shown all it's going to show as far as the star. If you are still seeing pits on the surface, it may just be because of the quality of the stone, nothing you've done wrong and from the steps you've described, there's nothing more to do to get it any better. When I first started buying stones off the internet, I bout some mine run rubies and tried tumbling them and soon found out that all rubies are not created equal!!! In fact, the ones I got were more like the type that are used to make corundum grinding wheels. Since I've gotten into cabbing, I've tried to see if I could actually make one of them into a gemstone by grinding, sanding and polishing it on my cabbing machine, but, so far, no such luck.
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Post by larrywyland3 on Apr 21, 2008 7:22:50 GMT -5
The dome look plenty high. You got a nice star. From the ones I bought some had bigger stars and some didn't even have any well defined stars like yours. Thats the problem with buying over the internet.
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Gem'n I
freely admits to licking rocks
Member since March 2008
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Post by Gem'n I on Apr 22, 2008 18:20:47 GMT -5
Here's my 2c...all rubies are not the same...one of the ways they differ is in the size of the striations...the smaller in diameter the striation is the weaker the star and vice versa. It appears you have one which has striations that are small in diameter hence the star falls off quickly....one with larger diameter striations would carry further down the dome of the stone...I am fairly certain the lot you bought from probably had a few people checking it before they release it "for sale". I think you did a very nice job with what you had...Larry
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Post by Tony W on Apr 23, 2008 1:28:03 GMT -5
Thanks for the link! I checked out his rough but couldn't find any pics that weren't blurred. How close was your rough to what you thought you were getting? It was odd as stuff in the background of his pics was in focus but the stones were not. T
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dshalldms
starting to spend too much on rocks
Member since January 2008
Posts: 113
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Post by dshalldms on Apr 23, 2008 4:17:55 GMT -5
Hi,
Having read all of the replies to your question,I would like to make the following
observations...
You are probably at the end of a chain of high grader's, all of whom would have been
looking for star grade material.
What is left can be regarded as low grade material as far as Star Quality is concerned.
However, all is not lost...
A well cut ruby cab can be a joy to behold, star or no star. Work on producing a high
grade cabochon, if a star appears, that's a bonus.
Having worked for 14hrs on a stone, 10 of which are at the polishing stage, I can only
suggest that you review your procedures.
To spend time polishing a stone that is not yet ready to be polished will only reveal
incomplete earlier stages of the process.
Looking at your photographs shows that you have made a great effort, I think the
material you have will make some beautiful cabs.
Keep up the good work,
Derek
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 23, 2008 11:39:50 GMT -5
Thanks all for the input!
I have been buying slightly lower grade rough with star possibilities to practice on until I get the hang of doing this... (before trying a more expensive stone).
Tony - the seller can't take macro photos at all it seems. The stones were fairlly accurately represented... some had healed fractures or pitted surfaces... but not many - overall very nice for the price... no 'clear' stones & none are RED... but they are nice.
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dshalldms
starting to spend too much on rocks
Member since January 2008
Posts: 113
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Post by dshalldms on Apr 26, 2008 2:03:04 GMT -5
This is a copy of a post that I found on another forum...
Traditional cutting, of which I don't approve, involves hunting
for the star by cutting a sort of sphere shape and then sanding
it. As the surface gets smooth the star starts to show, the
stone is now dopped and properly shaped, sanded and polished to
completion.
To get the best recovery you need to find the correct orientation
before you remove any material. The best answer is Star
Refractol. This is a thick fluid that forms a high drop on the
rough. The drop is viewed with a single overhead light source
and the star will appear on the drop. The orientation of the
star on the drop shows you where it will show on your finished
stone. Check your orientation with another drop of refractol and
when you have a star perfectly centred in your drop you have
found the apex of your hemisphere. Happy cabbing.
If you find that a little confusing, the instructions that come
with the bottle of Star Refractol has diagrams and explicit
instructions for use. If you do understand the principle then
you may be able to make do with glycerin but it doesn't work as
well. I would experiment before I spent money though.
Finding the star and making a good looking cab is the easy part,
the fun starts when you want to polish it. 'Star cups' are
certainly helpful for getting good shape and a useful pre-polish.
I also have a 'Corian' lap with a couple of shallow rounded
grooves that I cut into it. I use 8,000 diamond and it produces
a very serviceable prepolish that can be brought to a quick
polish with 14K and 50K pads.
Biggest problem is keeping the stone cool enough to keep the wax
from letting go. I use aluminium dop sticks which helps and
little pauses between polishing strokes stops the heat from
building too rapidly. You will have stones come off and you will
be on your hands and knees. Enjoy.
Hope this helps,
Derek
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ljhemmer
off to a rocking start
Member since April 2008
Posts: 14
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Post by ljhemmer on Apr 26, 2008 12:53:37 GMT -5
Hey Derek, thanks for posting that info from the other forum... it was very helpful & informative. I think I will look into getting some of the Star Refractol, it sounds like a good idea. Again, much appreciated!!
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