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Techniques for CollectorsDoes CZ Lose Its Sparkle?

27th Jul 2010 12:06 UTCRay Wilson

In a long winding thread on Fakes discussion board regarding Diamond Nexus Labs there was a comment made that CZ will become cloudy over time. The reason given was that CZ is oxygen deficient and it will absorb oxygen from the atmosphere causing it to become cloudy. This was something I had never heard of and have asked quite a few facetors since I saw the original post but none of them are familiar with the issue.

My question, perhaps to other facetors, is are you aware of this issue or does anyone have any experience with this. Our club runs faceting courses for beginners and has moved from using topaz to using CZ to avoid cleavage problems for the newbies, but if CZ goes cloudy we might review that direction.

28th Jul 2010 04:55 UTCJamey Swisher

CZ did used to do this over time, and some cheaper stuff still will. But other better chemicals and such are now added into the mix to make the CZ more stable and for its longevity. CZ is Zirconium oxide. The additives are typically plus yttrium or calcium, with, if my memory holds true, yttrium being the better of the two flavors of CZ but the Ca variant having slightly higher dispersion.

All CZ needs these additives in it to even from the crystals and grow in the lab. I believe where the issues occurred in the older stuff was the additives they were using back then, but I could be wrong.

Now, CZ is only an 8.5 on the mohs scale of hardness, so I guess over time it could get scratched up a bit, but not really much more then a topaz would. This could, if scratched enough, effect the clarity and make it look cloudy, but a simple repolish of the table will fix that anyways.

I know the CZ we purchase to use for cutting is guaranteed by the manufacturer NOT to cloud. Does it? No clue, haven't had any do so to date, but that does not mean it won't.

But the key factor here is too, if you spend $10-$25 on a 1ct CZ commercial cut and it lasts 10-20yrs, is that not a good deal? Just buy another and have the old one removed and the new one put in. Or even if spend $50-$250 on a 1ct custom fancy cut CZ from a good USA cutter and it lasts 10-20yrs+, is that still not a great deal in comparison? ;)

Edit: Some scientific, but easy to read and understand, info on CZ and how it is made in case you want to read about it.

http://www.geologyrocks.co.uk/tutorials/cubic_zirconia

31st Jul 2010 03:11 UTCRay Wilson

Thanks Jamey. Great article on geologyrocks website also.

Personally if I was going to spend over $50 on a coloured CZ I think I would be looking for a spinel, tourmaline, sapphire or beryl as an alternative. Probably different if youu're after a clear stone with nice sparkle though.

2nd Aug 2010 06:43 UTCJamey Swisher

If looking for clear stone with nice sparkle, white zircon, natural, and sparkles like a diamond far more realistically then CZ does IMHO.

13th Aug 2010 13:37 UTCRay Wilson

Jamey Swisher Wrote:

-------------------------------------------------------

> If looking for clear stone with nice sparkle,

> white zircon, natural, and sparkles like a diamond

> far more realistically then CZ does IMHO.

Jamey,

Would you use a zircon in a dress ring? Our jewellery instructor does not like using zircons in rings because of their brittleness and propensity to chip.

Ray.

14th Aug 2010 04:24 UTCJamey Swisher

Ray Wilson Wrote:

-------------------------------------------------------

> Jamey,

> Would you use a zircon in a dress ring? Our

> jewellery instructor does not like using zircons

> in rings because of their brittleness and

> propensity to chip.

> Ray.

Ray,

Jen has set and used Zircons in many rings and never has had one come back yet for any kind of repairs. Many settings can protect a stone, you just have to pick the right one. ;). Champagne colored zircon seems to be a fav folks get in solitaires from here for engagement rings and such. When you really think about it, a diamond, while far harder, is far more prone to chipping and breaking then a natural zircon is and they use them everyday in rings, and not very protected ones either, lol. Just use the same care with Zircon as you do with a diamond and you should be fine.

But this is just my opinion.

Jamey

22nd Aug 2010 00:35 UTCDon Saathoff Expert

Hello all. This is really stupid, but every time I scan this forum and see the title of this thread, I can't keep the lyric of an old popular song from popping into my head......"Does your chewing gum lose it's flavor on the bedpost overnight?"........sorry, just had to get that off my chest.....

Don S.

22nd Aug 2010 06:37 UTCJamey Swisher

ROFLMFAO!!! You weren't the only one Don!!! Same thing went through my head as well.

22nd Aug 2010 19:31 UTCRay Hill Expert

The other part of the story is that if your CZ seems cloudy, it might just need a good cleaning...

Diamonds can get googe collecting on the back of the stone and still sparkle, but CZs and other simulants dull up quickly if their backs get dirty.. Diamond has quite a natural attraction to grease and oils such as those in make up and cosmetics and it can dull due to a thin film of oils, and in both cases a bit of working away at the stone and under the setting with an old toothbrush and sudsy ammonia cleaner and a bit of hot water will clear it up

24th Aug 2010 03:46 UTCJamey Swisher

I would NEVER use any kind of chemicals on ANY gemstone to clean it or otherwise. Ammonia and other chemicals can have adverse affects on the stone if it is coated or clarity enhanced or surface filled, which many many stones and diamonds are on the market, many not disclosed properly.

Your best bet is simply to use an old soft bristled toothbrush and what I found to work great is the foaming hand sanitizing soap, make sure it is the soap, not that no water hand gel stuff! And use warm, not hot, water as some materials can react adversely to temperature shocks.

29th Nov 2010 06:51 UTCdebby

I have had my CZ for 11-12 years and has obtained a few scratches but the stone is round and it looks like it has a round etching on the very top where it starts to slope. Looks like the solitary in diamonds. It has lost its sparkle and wondering if or what I could use to bring the luster back. It is set in a very heavy 14 kt gold band. If I need to replace it, where should I go and how much to expect for cost. Approx 8 mm in 6 prong setting. Do jewelers mind doing this type of work?

Thanks!!!

29th Nov 2010 07:59 UTCRay Hill Expert

I have seen a lot of simulants, Debby, as well as some softer natural stones, , where the top rim edge looks cloudy and this is usually due to wear and tear on the stone, and the only cure, , is repolishing and possibly actually recutting...

30th Nov 2010 07:29 UTCRock Currier Expert

Have you cleaned the stone and ring throughly?

17th Jun 2012 04:48 UTCGerald Wells

The best advice I can give you is don't worry too much about a CZ. They are cheap, just change them.

17th Jun 2012 15:35 UTCOwen Lewis

I've read this resuscitated thread with interest. CZ is a fascinating material that is often mis-represented, as the quoted article exemplifies.A better short and basic guide to the properties of CZ is at http://en.wikipedia.org/wiki/Zirconium_dioxide .

CZ generally starts its life as Zircon sand. There are large deposits of this, one of which can be examined in some detail by using GoogleMap and is located just north of the port of Richards Bay in KwaZulu Natal. It's a large area of strip mining just behind the tidal beach. The Zircon sand, ZrSiO4 is converted to ZrO2 powder as a preliminary to the manufacture of the cubic crystalline form.This powder is ZrO2 in its tetragonal phase, which, I think, is unknown in nature

ZrO2 has three physical phases. These are monoclinic, tetragonal and cubic. \the only naturally occuring crystals are of the monoclinic phase (Baddeleyite). Baddeleyite is not tetragonal as given in the cited reference.

CZ is produced by melting tetragonal ZrO2 and allowing the melt to cool slowly, As it does so the melt crystalises in the cubic phase. However, pure CZ is not stable and, as its cooling progresses further, the cubic crystals revert to tetragonal phase, i.e. the large cubic crystals disinegrate into white powder once more. This regression to a state stable at room temperature can be arrested by doping the melt with a small percentage of certain metallic oxides, the oxides of Yttrium, Calcium and Magnesium being the ones cited. In this way, ZrO2 is produced that is stable at room temperature in the cubic phase. The dopant used and the percentage of the dopant will vary according to the intended use for the cubic product.

The doping process has become quite clever - a form of nanotechnology. An important nanoengineering variant is to toughen the CZ by producing a controlled admixture of nanometric lenticular tetragonal crystals in the CZ matrix. This can be arranged so that an incipient crack in a treated CZ crystal tends to be self-healing, preventing a crack from propagating.

The true hardness of CZ is surrounded by uncertainty and, one suspects the unwillingness of the gem trade to give publicity to improvements on the properies of CZ gems. Nanoscale scratch testing carried out in Russia as long ago as the '80s (published in the West in the early '90s - now twenty years ago - produced results showng that CZ (of unstated composition) can be appreciably harder than Corundum.

As with YAG and certain other manufactured compounds, CZ was first developed inductrially for military uses. The cited ref is also mistaken on several point here:

- Natural Ruby is commonly unsuitable for use in lasers (too many inclusions). Synthetic rubies are so used (ISTR that the first effective laser utilised a synthetic ruby).

- YAG is another manufactured compound which was, in that case, created to produce improved lasers for military applications. The gem trade adoption of these compounds is but a minor spin-off.

- AFAIK, CZ has never been used utilised on an industrial scale for lasing light. Rather it *was* first applied to production of transparent windows in low altitude hypersonic vehicles for guidance systems to look through. Rather more recently Apple explored the ideal of constructing the shells of the i-phone in coloured CZ to give both scratch resistance and transparency to emr

Research into the transparency of some technical ceramics and also their potential for both great hardness and toughness continues. Transparent armour is one goal.

As a gemstone, I think CZ is a wonderful material. It suffers for reasons beyond the scope of discussion here but which include cutting and polishing of less-than optimal quality. Cut to dimensions optimised for its own optical properties and expertly executed, the results stand alongside those attained with any of the tradition great gemstones. It stands on its own merits and not as it is commonly perceived, 'the best Diamond simulant'.

17th Jun 2012 17:00 UTCJohn M Stolz Expert

This was a super-informative thread guys--thanks

John

28th Jun 2016 15:59 UTCDiana Price

someone mentioned something about an amonia cleaner... How do you mix it

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