I recently got a hold of a couple pieces of Moissanite rough.
These pieces are supposed to be 9 carat H4 silicon carbide, in the DEF colour range (though they don't look like it).
I was warned by the seller prior to the purchase that cutting Moissanite normally would yield brown stones but that they offered a heat treat and CVD process to return the stones to the DEF colour range. The pictures they provided of the the stones they produced (supposedly from the same quality of rough they sold me) looked great after the heat treat and CVD post processing so I'm hoping I didn't get tricked...
Anyways, I'd like to know if there are any tips or things to watch out for when cutting Moissanite. Any advice at all would be appreciated as these weren't exactly cheap and I'd like to get some good stones from them. What would you guys suggest I use to cut these stones?
Joined: Fri Jun 25, 2010 10:06 pm Posts: 2267 Location: Chapel Hill, NC / Toronto, ON
Some quick tips:
1) Cuts like sapphire, but slower, with no orange peel 2) Gets super hot during polishing depending on how you do it 3) Can turn super brown during polishing for some of the different polymorphs or depending on the impurities 4) The treatment really, REALLY does a good job of whitening the material
Thanks for responding to me, I was getting worried I would have to cut them blind and learn on the fly.
I did a quick test polish of one of the sides by hand and I did notice dirty brown swarf (as opposed to milky white for pretty much any other stone) coming off the cutting laps. The side i polished still ended up quite brown regardless of my attempts to keep the stone cool.
Well, I guess I'll cut them and have them sent out for treatment. If all goes well maybe there will be another trustworthy source for small quantities of rough Moissanite for everyone.
Joined: Thu May 29, 2008 8:32 am Posts: 1730 Location: Suwanee, GA US
lightbender57 wrote:
Who does the heat treatment????
Me too. I want to know. I like the material, but just waiting for the price drop.
In the meantime, going to start playing with "Monosital"*
* copied from their page - Monosital™ belongs to material group which is called glass-ceramics. I.e. it’s the composite material that contains very small ( nano-sized) crystals into glass matrix. Glass-ceramics is the combination of glass and mono crystals. The glass matrix has Y-Al-Si-O and crystal phase may be different. It depends on required color: garnet, mullite, cordierite (dichroite) , etc. The last composition definitely allows achieving the best optical index. Even though there is no any combinations Pb (lead) and that’s why we can make high dispersion 0,015-0,02 and refraction index ( to 1,75). It’s achieved because of Y and Al as in case with crystals YAG. We’re improving these indexes but the color is unchangeable. For example, we produced blue and orange sapphire with density of 3,6gr/cm3 and RI – 1,75, i.e. it’s like natural sapphire.
Joined: Tue Jun 12, 2007 6:41 pm Posts: 5534 Location: Massachusetts, USA
I just got though cutting a bunch of Nanosital. It is the easiest material to cut and polish I have ever seen, and would be a wonderful confidence building stone for beginners.
72 Index:
RI varies with color somewhat..vaguely around tourmaline. Not much dispersion, though, but takes a mirror polish instantly. Anything polishes it easily.
Joined: Sun Aug 21, 2016 7:39 am Posts: 228 Location: Long Island NY, USA
Gearloose wrote:
I just got though cutting a bunch of Nanosital. It is the easiest material to cut and polish I have ever seen, and would be a wonderful confidence building stone for beginners.
72 Index:
RI varies with color somewhat..vaguely around tourmaline. Not much dispersion, though, but takes a mirror polish instantly. Anything polishes it easily.
Joined: Thu May 29, 2008 8:32 am Posts: 1730 Location: Suwanee, GA US
Tygurrr-I wrote:
Gearloose wrote:
I just got though cutting a bunch of Nanosital. It is the easiest material to cut and polish I have ever seen, and would be a wonderful confidence building stone for beginners.
72 Index:
RI varies with color somewhat..vaguely around tourmaline. Not much dispersion, though, but takes a mirror polish instantly. Anything polishes it easily.
Joined: Sun Aug 21, 2016 7:39 am Posts: 228 Location: Long Island NY, USA
gsellis wrote:
Tygurrr-I wrote:
Gearloose wrote:
I just got though cutting a bunch of Nanosital. It is the easiest material to cut and polish I have ever seen, and would be a wonderful confidence building stone for beginners.
72 Index:
RI varies with color somewhat..vaguely around tourmaline. Not much dispersion, though, but takes a mirror polish instantly. Anything polishes it easily.
Ha? No, no, I wanted to know the size of the stone.....many times, when I view fellow forum members work, I tend to envision their work in jewelry designs that I make up on the spot in my mind
That being said, I'm loving the CC material you just showed me! Thanks!
Joined: Thu Jan 24, 2008 4:01 pm Posts: 1902 Location: Pine City, NY and Dothan, AL
You can even get the material from Amazon. Seems to run 40 or 50 cents per gram.
The manufacturer, RusGems, describes it as "a multi-component high temperature composition on the base of two main oxides – SiO2 and Al2O3". They call it a glass, but they also say it's polycrystalline. It actually appears to be amorphous. Maybe something lost in the translation from Russian.
1) Cuts like sapphire, but slower, with no orange peel 2) Gets super hot during polishing depending on how you do it 3) Can turn super brown during polishing for some of the different polymorphs or depending on the impurities 4) The treatment really, REALLY does a good job of whitening the material
I recently cut a Moissanite. It was much easier than I thought. I used 260 grit for preforming and 600 grit for cutting. I used a Dominatrix lap (outer band) with 8k PCD for prepolishing and a Dominatrix lap (inner band) with 100k PCD for polishing. My biggest surprise was the total absence of heat during prepolishing and polishing. Since PCD can be used with water, this probably made things easier (water conducts less heat than oil). The transfer was done cold, without using any heat source. Since no heat was generated during the cutting and transfer, the stone did not change color. It was very slightly yellowish in its rough state and stayed that way throughout the cutting process. I am really happy with the result.
Now there is one question I need to answer. What is the heat treatment used to remove the yellow tones seen after the cut. I contacted a Moissanite cutter who lives in Italy. He gave me the following procedure. He has never used it personally. So I don't know if I can trust it.
The stone is placed in an oven. The temperature is raised to 600 degrees Celsius, at a rate of 50 Celsius per hour for the first 150 degrees, and 20 Celsius per hour for the next 450 degrees. This temperature level (600 Celsius) is kept for 6 hours. We then cool down at a rate of 20 Celsius per hour.
This procedure is really very simple. It is a bit long but it is probably designed to avoid thermal shocks. Not having an oven that can be programmed with such precision, I tried to find an individual or a company that treats Moissanites to improve their color. Unfortunately, it seems to be a very well-kept secret. If you know of anyone or a company that offer this service, your help would be greatly appreciated.
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