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Author Topic: Polishing zircon  (Read 2182 times)

Faceting Frank

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Polishing zircon
« on: September 27, 2019, 04:43:19 PM »
My very first question on the forum and that is on how to polish Zircon.
I want to enter next years Ozzy facetors guild comp. and one of the stones is a cushion shaped zircon. I bought a piece of rough off eBay weighing just under six carats the right shape and it’s just big enough for the job. It’s capable of producing a stone with a girdle of 6.5mm X 6.3mm minus pre-polish and polish. It has plenty of depth at 5mm.
So I will have to cut and polish the girdle first to ensure I keep the stone above the 6mm minimum size, so I have no room for stuff ups.
I normally use 3000 and 60k diamond on Batt laps for pre polish and polish on Topaz, Zirconia etc. but don’t know what to use on the Zircon. I have a Darkside lap if that’s any use.

Thanks

Rusted

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Re: Polishing zircon
« Reply #1 on: September 28, 2019, 02:28:08 AM »
Use what you've got. I have never had trouble polishing Zircon.

FlashGP

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Re: Polishing zircon
« Reply #2 on: October 01, 2019, 06:07:12 PM »
Hi Frank,

Batt or Darkside with diamond on them will polish zircon.

Great to hear you are going to enter the competition.

If you are a member of a lapidary club, you should gave ready access to the competition rules.  Read the bit about judging features.  It'll give you oointers as to what the judge looks for.

There are also judging sheets at the end of each section that tell you how the judges allocate points for each group.

I encourage competitors with queries on interpretation of the rules to post them on the AFG forum, I get updates so we can see when queries come in.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: Polishing zircon
« Reply #3 on: October 01, 2019, 07:19:15 PM »
Hi FlashGP,
It’s good that Batt laps and diamond will polish Zircon, very easy to use and produces a great finish.
I’ve entered the AFG open comp a few times now and came  4th in last year’s comp. and came 1st in the Freeform cut.  So I know how tough the judging is.
Meet points I think are perfect through a 10x loop aren’t as far as the judges are concerned. Some of them I loose points through, so bought myself a 30x loop to do a final check over with. Also a more versatile lamp, as getting the right reflection to be able to see flaws in the polish is a must have.
No good taking the stone out of the chuck and spotting problems.

FlashGP

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Re: Polishing zircon
« Reply #4 on: October 02, 2019, 07:51:47 AM »
Hi Frank,

I hsve a 30x,60x loupe but stopped using it when I bought my Belmo 10x alplanic loupe.  It is what the judges use and os as strong as a 30x plastic loupe.

Lighting is an issue for competition faceting.  You want a pinpoint light to reflect off the facet, then take the facet just off reflection and scratches will light up.  But you want a light over your shoulder for seeing the facet boundaries and facet shape.

I use an LED light in a gooseneck from Ikea, and my wife's needlework light, which is a standard lamp for over my sholder.

Look at the facet shape of each facet where they meet the meetpoint.  When they are all pointy, the meetpoint is met.

I believe you live just north of Brisbane.
If you are a member of the Facetors Guild, we have a meeting of the Moreton Bay Facetors Group this Sunday morning. At the club rooms for the Mitchelton Lapidary Club at the old Scout Hut at 40 Fernydell st, Ashgrove, starts at 9.30am.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: Polishing zircon
« Reply #5 on: October 02, 2019, 10:38:35 AM »
Looked for that loupe on eBay Gordon but could not find it, I take it it’s an upmarket model.
I have my machine on a desk only 1/2mtr away from a window, that light comes from the side and I can reflect it off the facet as well as the lamp light.

Prooz

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Re: Polishing zircon
« Reply #6 on: October 02, 2019, 06:24:42 PM »
Looked for that loupe on eBay Gordon but could not find it, I take it it’s an upmarket model.
I have my machine on a desk only 1/2mtr away from a window, that light comes from the side and I can reflect it off the facet as well as the lamp light.

Google, 10 x Belmo Alplanic Loupe. Worked for me

Dihusky

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Re: Polishing zircon
« Reply #7 on: October 02, 2019, 06:51:35 PM »
Belomo loops are available from Pilbara Geology, think they are the importers.

As for lighting, the judging requirement for examining gems is a 40w incandescent, as these are hart to get I believe they now use the globes with the little halogen inside. If you use an LED globe you should see everything. It's worth getting the AFG book on judging gems as it gives all the info you need for hitting the mark on comp stones.

Faceting Frank

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Re: Polishing zircon
« Reply #8 on: October 02, 2019, 08:03:11 PM »
Ah, they are those head band loupes.

FlashGP

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Re: Polishing zircon
« Reply #9 on: October 03, 2019, 07:01:22 AM »
Hi Frank, no, the 10x headband loupe is neasured differently, it is about 3x in an eye loupe.  The Belmo loupe has a 21 mm triplet lense that is ground to magnify a grid pattern with straight lines.  That is, its aspherically ground like a camera lense to minimise aberations away from the centre of the field of view.

Mine cost about $50 from Rubyvale cut and slice, and I think so does Pilbara Mining Supplies in WA.
 
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: Polishing zircon
« Reply #10 on: October 03, 2019, 04:29:25 PM »
Thanks for that info Gordon. I have purchased one from Max at Rubyvale.

Aussie Sapphire

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Re: Polishing zircon
« Reply #11 on: October 05, 2019, 07:50:12 AM »
Hi Frank, no, the 10x headband loupe is neasured differently, it is about 3x in an eye loupe. 

When looking at the Donegan Optivisors (headband loupe), the lens are are marked in dioptre values which is NOT the same as magnification.  This can cause a lot of confusion with people when they think their DA10 Optivisor should mean x10 magnification.
As Flash notes, a dioptre value of 10 is equivalent to about x3.5 magnification.

When buying a loupe of any kind, make sure you know which system is being used.  Most manufacturers use magnification power which is simple to understand but there are a few (including Donegan) who use Dioptre value instead and the numbers are not the same.


Also keep in mind that if a x10 loupe works well, a x20 loupe will not be twice as good.  Tempting to think that stronger magnification is automatically better but you need to pick the strength to suit the job you are doing.  Stronger magnification means a smaller depth of field so more difficult to keep the item in focus.  Of course for competition cutting, you need good magnification to see quality of polish but for general faceting, a good quality x10 loupe is the common choice as it hits that sweet spot between good magnification and ease of use. 


Most cutters will have a range of options as they work though - head loupe while they are cutting and a hand loupe for closer checking.


cheers
Leah
« Last Edit: October 05, 2019, 07:54:52 AM by Aussie Sapphire »
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Prooz

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Re: Polishing zircon
« Reply #12 on: October 05, 2019, 10:15:10 AM »
Good info thanks.

Faceting Frank

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Re: Polishing zircon
« Reply #13 on: October 05, 2019, 03:35:04 PM »
Hi Leah.
I use an Optivisor for general use and a 10x loupe, which I think I bought from you guys, for closer inspection. Should get the Belmo loupe mid next week. Just finished the pre-polish stage of a comp. stone, so will leave it till I get it.

FlashGP

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Re: Polishing zircon
« Reply #14 on: October 08, 2019, 08:42:11 AM »
Hi Frank,

When checking the pre polish and polish, reflect the light from a single point light source off the facet, then move it just foo the reflection, the scratches should stand out.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

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