What is this stuff, and why are they advertising it in movie theaters? Looks like fake diamonds to me, but the moissanite.com site refuses to cooperate with my browser, and I refuse to switch browsers just for their sake.
Moissanite faqs. It is single-crystal silicon carbide, discovered by and named for the famous French chemist Henri Moissan.
Interestingly, silicon carbide (also called carborundum) was first produced in 1891 by Edward Acheson when he was trying to make artificial diamonds. Moissan discovered the first natural occurrence of the mineral (in 1904-5?). One of the early uses of the stuff was for polishing, including sandpaper.
That’s still one of the major uses. It’s also used in many hand tools: Ever hear reference to, say, a carbide-tipped screwdriver? That’s silicon carbide, although admittedly synthetic and far from gem-quality. The stuff is almost as hard as diamond, ranking somewhere around 9.6 on the Mohs Hardness Scale (I think… My copy of the Handbook of Chemistry and Physics is up at the office).
Commercially produced silicon carbide is sometimes sold in chunks at gem and jewel shows as a curiosity. It is very beautiful, in dark peacock colors (green, purples) and black. Specimens sometimes have large (eg., half inch)
,flat, hexagons sticking out, which are apparently single crystals. Both carbon (which is what diamond is) and silicon come in tetrahedra, ie., think of a tetrahedron and each point being a carbon atom, and this is diamond, only the structure is repeated over and over until it is large enough to sell. I suppose silicon atoms bond to each other the same way. Where the silicon atoms and the carbon atoms are on the tetrahedra they never tell you. Silicon carbide specimens are desirable but dangerous, as they are very sharp and tiny pieces fall from them onto the floor where you can step. I got a chunk a foot and a half long onetime. It was found in the back yard of a place that used to produce silicon carbide (aka carborundum) as abrasive. However, I don’t know if they use it anymore for anything.
Museum shops sell small pieces of it in little boxes as part of their mineral offerings. The article on moissanite from that place that sells it denigrates (disses) cubic zirconia, but that is also a very beautiful stone when cut sharp and well. Jewellers hate it because it is easy and cheap to produce–the cost is all in who cuts it and how. A double cut stone rectangle about a half inch long can be a hundred bucks, but you can get bigger ones, even, for less but they are not sharp or even evenly cut. Always look at the back of stones to see if they bothered to cut them symmetrically, I always say. The general public has been trained to laugh at cubic zirconia, but it is more beautiful than diamond. However, the general public is incapable of valuing anything unless it costs lots of money.
We purchase diamonds and jewelry over our counter from the public. The three of us who buy have no problem visually distinguishing a diamond from a cubic zirconia. For the one in a thousand CZ which has that “gee, is this fake or real” look, we have a thermal conductivity tester which beeps when the probe touches a real diamond. No beep=CZ.
But now comes Moissanite. It makes a thermal conductivity tester beep. Scary.
So, we now have a Moissanite detector. It can distinguish between a diamond and a Moissanite. Again, by beeping or not beeping. Takes 5 seconds.
The really scary stuff is just now starting to happen. They are close to perfecting lab-grown diamonds. When this happens, eek!
Two questions: First, what is the thermal conductivity of sapphire? (Not necessarily the gem, just any large crystal of aluminum oxide). Second, a few years ago I’d heard that it was theorized that a certain configuration of carbon and nitrogen atoms (carbon-beta nitride, or something like that?) might be harder than diamond. Has anyone synthesized this compound yet?
Answered my own question Thermal Properties of Materials
Usually whenever I search for anything, I get either zero hits or 25,558. I’m amazed I actually found this.
I was surprised that sapphire has such a low conductivity compared to metals. I thought if diamonds were good heat conductors then maybe all covalent crystals were. There goes my plan to market fused-alumina cookware. 
I just learned from a jeweller that the detector that can discriminate between diamond and moissanite costs 600 dollars. I bought at a gem show a beautiful stone that the dealer said was a diamond simulant, carbon based. It was a reasonable price, in fact if it is moissanite it was a bargain. I also ran across a jeweller recently who has been in business forty years, and is respectable, as they say. As far as I know. But respectable doesn’t necessarily mean knowledgeable.I seldom run across a dealer who knows that gems are made out of atoms of particular elements. My latest glaring example is I was shown a nice green stone and it was too large to be a natural stone, so I asked was it synthesized (manufactured) out of corundum, and the jeweller said yes, but then he looked at the label and said no it’s spinel, “That’s what I thought,” he said, “man-made corundum-spinel.” Corundum is the name for aluminum oxide in the I believe hexagonal crystal system, which is exactly what rubies and sapphires are and also the abrasive. Corundum is sort of a generic term for sapphires and rubies of any quality and for the abrasive. Spinel is magnesium aluminum oxide, found in nature in some crystal system as material from which the spinel gems are cut and can be many colors. To manufacture gems from spinel they take the magnesium aluminum oxide and put in extra magnesium and use heat like they do with manufacturing gems from corundum material. A large crystal forms and from that they cut beautiful stones which differ from the ones created by nature only in being flawless. Those big red rubies men used to wear in gold rings are examples of nice synthetized corundum. There’s no such thing as spinel-corundum. When buying gems it’s like buying anything else. You have to get knowledge yourself because the average sales person is into SALES and seldom KNOWS anything substantial about his or her product. They aren’t allowed to lie but they can’t be made to tell the whole truth either. Florists aren’t botanists,
insurance companies aren’t humanitarians, and gem dealers aren’t gemologists, and neither are gemologists, for the most part, in the sense of knowing crystallography. Almost all gems you buy have been dyed, radiated, coated, heated up, imbued with plastic, soaked in chemicals, synthesized in the first place–ie., depending on the stone one or more of the above. If you ask a dealer or jeweller, now is this diamond coated? They don’t know. Back in the storeroom there is probably a record of this, but not necessarily.
They’ll tell you a stone is synthetic, which to some of them includes glass, so the trade has tried to change the term to man-made. If you ask if a stone is man-made the salesperson will say if it is, once they ask the boss, who may or may not be there, if it is man-made. But if you ask is it corundum or spinel, the two most commonly used materials, they will say they don’t know. Beware of the new alexandrites coming out. I was told by one dealer that a nice big alexandrite was a man-made one, and I said oh is it made from berylium aluminum oxide, which is what natural alexandrites are made of, and he said no it’s just quartz. No problem, like most dealers he is honest, and it was a beautiful and expensive stone, flashing red and green. Another dealer had similar “alexandrites” and these, he said, were just man-crystallized corundum. This made me wonder whether, though honest, these dealers knew what material they had, since it seems unlikely that two different substances would be used to make these beautiful stones. However, it is possible and I for one am glad they are producing them. They aren’t just those coated topazes either. One dealer I encountered had wonderful faceted stones in a wide variety of sparkling colors, and I said what are these? He said with pride, “carborundum,” which brings us back to moissanite, the clear diamond-like substitute for diamonds. But carborundum or moissanite are silicon carbide, and I thought my goodness, that would be wonderful to have gems in all these colors, nice big ones, and made out of such a hard material second only to diamond in hardness. Well I finally got him to say they were (very well cut) glass, but he added, “that’s what glass is, carborundum.” I could give more examples but here are more warnings: I understand that topaz often comes in crystals several feet long and often clear. One company has been selling cut clear topazes under a special name I think they have patented, and they are very nice stones but also should not cost very much because they are common. Almost all the blue topaz you buy are treated clear or other topaz material, in other words treated aluminum hydroxyl fluoride, which is what natural topaz is. They don’t man-make topaz because it is so common that they just get the natural thing and either heat it up or radiate it to get the desired color. Of course everybody knows that the yellow gem known as citrine, which is quartz or silicon dioxide, have been called topazes, so now the trade uses the term “imperial topaz” when they mean aluminum hydroxyl fluoride. Evidently the ametrine, which is half citrine and half amethyst and all quartz, since amethyst is purple quartz, was found in nature, but they have since figured out how to create ametrines in the factory. Oh I amost forgot: watch out for all those tanzanites flooding the market: there are some very beautiful man-made versions and the dealers themselves might not know what they have. As a sales person, a dealer in anything often buys substances which nobody knows what they are without testing, and why bother with testing. Where the honest comes in is they have to tell you they don’t know what it is, and then it is up to you.You can often pick up some stunning bargains in such material. My latest purchase was a very reasonable YAG, another diamond-lookalike made out of yttrium, aluminum, and evidently garnet material, which is in turnmade out of lots of elements that can vary. They don’t make YAG much anymore, or a wonderful multicolor-on-clear synthetic titanium oxide stone called titania, or another one known as fabulite, unfortunately. These are now curiosities and I would much rather have them than diamonds, which are so common. One further warning: lights in gem shows and in jewellers are very bright and normally you don’t go about in such light. And I have bought things under “special” lights that are quite dull under any other kind of bulb, but these weren’t gems, but fluorite specimens. But they didn’t cost much and wound up in the rock garden. Caveat emptor.
$600 for a moissanite tester, huh? Funny, my M&M distributors catalog starts them out at $129.90, with their top dollar model at $145.90. Just a jeweler making his typical 400 percent markup. If you can pretend that you’re in the business, you can probably buy from M&M at http://www.mmwholesale.com.
FYI, I’m watching a PBS Nova show right now, about artificial diamonds. It is titled “The Diamond Deception” and should rerun a couple of times this week.
Good info don, but for the love of God, please please use the friggin return key once in a while. 
In writing e-mail if I press tab to make a paragraph, my computer obliterates a line or two of what I have written, so I am afraid to use anything but just keep typing along.
Now I’ll try on this: here comes tab–well that shot the screen way up. When I used to do this I thought all was lost and gave up before someone showed me the concept of scrolling, and if you scroll things are there! Now I’ll try the enter key:
ah that’s it. what about shift: nothing. Okay so it is enter: that works, but not enter and then tab, like you do on word processing where you just hit enter, tab, and you have indentation. On this whatever this is called I’m doing now, somehow tab means “suddently scroll down for no particular reason.”
I also keep a typewriter around which is my lap top typewriter to copy e-mail I’ve written or received when the computer is frozen and might lose it.
As for the PBS show on diamonds, it is fascinating and I saw it again myself last night (our PBS station has never had anything on it that WASN’T a rerun, which is a problem in logic that defies philosophy but is actually true, though in this case I’m glad because it is an entrancing show, the one on the diamonds and their substitutes. There is another PBS show that will be rerun someday on how they got the buying public to buy diamonds. I for one will be happywhen theycan synthesize diamonds that will be cheaper than the ones formed “100 miles beneath the earth.” There is too much pretentiousness and irrational behavior going on around diamonds. If people could only appreciate their beauty without demanding a mystique!
As I watched the De Beers hirelings going about with worried looks I was delighted. If oneday everybody didn’t have to give 100 mile below the earth diamonds it would be fine, and then we could get to work on how you have to give a dozen roses instead of anything else
Diamonds would already be much cheaper than they are, without synthetics, except for the artificial prices set by DeBeers. I don’t think synthetic diamonds will change much. DeBeers is already a leader in synthetic R&D, and their branding campaign (i.e. putting a brand name like “DeBeers” on a diamond) is designed to create an artificial demand for THEIR diamonds. Given their success over the last 60 years in shaping consumer demand, I wouldn’t be surpised if they flourish with synthetic diamonds also.
Synthetic emeralds didn’t drastically reduce the price for emeralds, either.
Arjuna34
I mean reduce the price for natural emeralds, of course
Arjuna34
:rolleyes:
I don’t think it’s going to fly. Maybe with lesser settings, but I believe that people in general will want the real deal FOR the real deal.
Think about it…white sapphires, no go. CZ, no go. Colored diamonds, for the most part, no go. (Blues and pinks, yes…but so called “canaries,” nope.) People have been conditioned by De Beers to think “a diamond is forever” and “the 4 C’s” mean everything.
I wonder…does De Beers artificially create the rarity of diamonds, just to drive the price up? Are there other gemstones that could be rarer? :rolleyes:
Yes, they do. DeBeers has huge stockpiles of rough stones, which they use to help control demand, and even out supply kinks when mines run dry. They have been known to buy up the output of competing mines, just to keep them off the open market.
In general, though, large polished diamonds are getting harder to find. That’s one reason for the relatively sudden increase in pave-style jewerly (where lots of very small diamonds are inlaid to create the sparkle of a large diamond), and jewelry with several small stones together (in pairs, groups of four, etc.).
Aren’t emeralds just as rare, if not rarer, than diamonds?
Arjuna34
I don’t know if they’re rarer, per se, since the influx of lab-created emeralds but it’s definitely harder to find a naturally occurring, flawless emerald.