Colored Gemstones

Engagement Ring buying advice and recommendations

This is my advice for someone looking to buy an engagement ring. I've done a lot of research into it, and listed what I thought are the most helpful links. This is an actual email that I sent to a friend who asked for some information.

Hi ----

I was thinking about your engagement ring for ----, so I wanted to send
you some helpful information.

The best forum that we have found for diamond and engagement ring
information is
People are really knowledgable there, and willing to help. So if you
wanted to, you could make an account and post your budget, desired
ring style, etc and people will help you get a good ring that fits in
your budget.

There is also a lot of good information there. This link is to the
Diamond Guide

They also have an engagement ring tutorial so you can get familiar
with the different styles of rings, important terminology, etc

I would recommend doing a little research on those forums. I think
that a 10k budget is a lot, you can get a really great ring in that
range. You may even end up spending less. Jeremy originally set a 10k
budget as well, but since we decided to go with sapphires, we are
anticipating spending about 5k for the engagement ring (stone &
setting). Diamond are more expensive, but I think you can get a really
nice diamond and setting in that budget.

I would recommend starting with a 1ct diamond, round brilliant cut.
You can go up in carat size if you feel comfortable, cut I think a 1
ct is a nice place to start. Do not look at colored diamonds or "fancy
diamonds". You cannot afford it. You should also stay above I think
the G color grade, b/c below that the diamonds start looking a little
yellow. I would check this though, bc I'm not completely sure, and the
cutoff may be different based on personal preference.

I would recommend you get the setting in platinum instead of white
gold. Platinum is more durable, and will not wear as much as white
gold. Platinum will need to be occasionally polished, but what I dont
like about white gold is that it is actually a yellow gold core that
is rhodium plated so it looks white. I don't like the idea of plated
things, and people on the forums say that the rhodium plate will wear
off as early as 6 months for some people, and the ring will show
yellowish color underneath. The rhodium plating may last for a few
years for some people with less wear on their rings. Platinum will
cost more than white gold. I would budget about 2k for a nice platinum
solitaire setting, so that leaves about 8k for the stone, which is
definitely reasonable. I do not recommend yellow gold unless you know
that is what she wants. Yellow gold has fallen out of favor, and is
not "trendy".

For ideas of ring styles, I would look at , ,
They have a large selection of rings, so you can look and see if there
are certain styles that would be best. I would focus on the solitaire
settings, because it is a really classic style. I'm not sure what -----
means by "vintage," if she actually wants an antique ring or something
1920s style or whatever. I would go with a solitaire if you are not

Do not buy from Tiffany & Co. Do not buy from Etsy. Tiffany is way
overpriced, and Etsy quality is questionable and often overpriced. Do
not buy from Zales or Jareds or any other mall store. Overpriced and
poor quality.

I'm not sure if there are any custom diamond cutters like there are
for colored stones. I was just thinking that the supply chain is so
tightly regulated, and diamonds are so expensive, that I doubt there
are any cutters that buy diamonds to recut. You might find a diamond
cutter if you look around, but I doubt it. However, all diamonds come
with a certification that describes how well it is cut. Cut is
actually pretty important of the 4C's, bc a lot of the brilliance and
scintillation of a diamond depends on the cut.

There are some really good custom ring makers, if you want to go the
custom route. Brian Gavin ( was one that I
was looking at for a while. Another good ring maker is Leon Mege
( Mark Morrell ( also does
really great custom rings and has a really great style.

If you want to order a custom ring, it will be a little more
expensive, and you will have to wait around 6 weeks for the product.
Usually the process goes like this - you contact the ring maker with a
specific idea of what you want made. They will clarify with you the
details of the ring, then make a CAD rendering of the ring and email
it to you. You can indicate changes that you want from the initial CAD
rendering, and it can go back and forth like this for a few drafts
until you are satisfied. The ring maker will then create a custom ring
mold to cast the ring in, then set the diamond in it, and you are

If you want to go the custom ring route, I would make sure you know
exactly what you want. I would save some pictures of ring styles
online that you want to incorporate elements of, or draw some
preliminary sketches to show the ring maker.

I hope this is helpful. I would do a little research on
first, then look at some engagement ring prices and styles on the
different websites I suggested. If you feel that there is no ring
style currently in production that you think ----- would like, or you
really want to give her a one of a kind unique ring, then I would
contact some of the custom ring makers. But make sure you have an idea
of what you want before you contact them, which is why I suggest
looking at sites with a nice wide selection of rings as a preliminary

When you buy the ring, make sure you get it appraised and insured. You can get insurance through an additional rider on your homeowner's insurance. Or you can get a separate jewelry insurance, which may offer more coverage. Either way you will need an independent appraisal. This is important in case of theft or loss, since it is such a big purchase.

Ok, I hope that information is helpful and not too overwhelming. If I
think of anything else, I'll send it to you later.

Are diamonds really rare? Myths and misconceptions about diamonds

Are diamonds really rare? Myths and misconceptions about diamonds

Diamonds are our most popular gemstone. That hasn’t always been the case. It was only in the the last century that diamonds became regularly available. Prior to that, rubies and sapphires were the most popular gems, especially for engagement rings.

The popularity of diamonds is due primarily to the DeBeers organization. They set up the first large scale diamond mines in South Africa. Then they began one of the most successful advertising campaigns in history, convincing consumers that engagement rings should have a diamond.

With proper encouragement, the movie industry displayed their most glamorous women, draped in diamonds. They soon became a top status symbol for the rich and famous. This peaked with the Marilyn Monroe movie, Diamonds are a Girls Best Friend.

Even after winning the consumers admiration, DeBeers continued their advertising. With the discovery of diamonds in the Soviet Union, a new campaign was created to sell anniversary bands. These made good use of the small, but nice quality diamonds the Soviet Union produced.

While they have done wonderful things for the diamond industry, not everything about DeBeers is nice. As diamonds were discovered in other parts of Africa and South America, DeBeers managed to get control of the rough diamond supply. The tactics used to gain control of these rough diamond supplies are alleged to include murder and kidnapping.

DeBeers maintained monopolistic control of the diamond market for several decades. They carefully released only enough rough for current demand, while continually adjusting the degree to which the rough was made available. This caused continually escalating prices, and of course, it increased the perception of rarity. DeBeers actually mined considerably more rough diamonds than they sold and they have a large warehouse of uncut diamonds in London. As a result, they were not allowed to do business in the US, Canada, and a few other countries.

In the last couple decades of the 20th century, things began to change. Satellite technology, that was designed to find likely oil reserves, also showed the geology likely to hold diamonds. As a result, new discoveries began to multiply. Australia was one of the first developed nations to discover major diamond resources. DeBeers was able to make a deal with them do distribute all the rough, except for the very rare pink diamonds.

They also made a deal with the Soviet Union to distribute their rough diamonds. However, shortly after the break up, the Russians let their contract expire and began to sell the diamonds themselves.

The latest major diamond reserve was found in Canada. DeBeers could not make a deal with the Canadians, who are cutting and selling the stones themselves.

It is difficult to tell what the future will hold. Several sites are being explored and it is likely more diamond deposits will be found in the near future. DeBeers still controls approximately 75% to 80% of the diamond rough. The other suppliers have so far been content to sell at the same prices as DeBeers. However, if the law of supply and demand ever catches up to the diamond market, prices are likely to drop considerably. It is difficult to tell how this would play out, but DeBeers has a large inventory of uncut diamonds and would be in an excellent position for a price war.

Myths and Misconceptions

Here are some popular myths that you need to be aware of.

MYTH: Diamonds are rare.

Diamonds are the hardest material found on earth. Other than that, they hold no unique distinctions. All gem grade materials are rare, composing just a tiny fraction of the earth. However, among gems, diamonds are actually the most common. If you doubt this ask yourself; “How many women do you know that do not own at least one diamond?” Now ask the same question about other gems.

While we are still learning about the interior of the earth, current information shows that diamonds are likely the most common gem in nature. (See “Gem Formation” in our Reference Library.)

Outside the earth, diamonds are also common. A recent discover shows that some stars collapse on themselves, creating giant diamond crystals. In the constellation Centaurus, there lies a white dwarf, that has crystallized into a diamond 2,500 miles in diameter and weighing 10 billion, trillion, trillion carats.

MYTH: Diamonds are the most valuable gem.

You cannot say that one species of gem is the most valuable. To do a comparison, you need to judge gems according to size and quality. This chart is based on top quality gems in different sizes. However, note that pure red rubies are so rare there is no trade data available. The prices listed are for Burmese rubies.

Species            ½ carat        1 carat       >1 carats
Diamond        $4,300/ct    $13,600/ct    $44,500/ct
Ruby              $5,050/ct    $9,500/ct     $100,00/ct
Emerald         $5,470/ct    $9,030/ct     $23,000/ct
Sapphire      $10,000/ct    $16,000/ct    $34,000/ct
Alexandrite    $3,600/ct    $15,000/ct    $1,000,000/ct

As you can see, diamonds are very costly, but not the most expensive gem in any size. If you were to do a comparison of other qualities, the results would be similar. If you are looking to “invest in gems” you should read our article on the inner workings of the gem trade.

MYTH: Diamonds are precious.

Precious means valuable. In the 18th century a French jeweler began describing gems as either precious or semiprecious. The categories are still used in merchandising, but are frowned upon by professionals as they are nearly meaningless distinctions.

For example, garnets are considered semiprecious, but tsavorite garnets have sold for as much as $10,000 per carat. That seems pretty “precious” to me!

On the other hand, diamonds are only very valuable in their better grades and medium to large sizes. Small, low quality diamonds are available in quantity for just $1 a piece. A quick search of eBay and you will find several diamonds under $20. These are far from precious.

MYTH: Diamonds are the most brilliant gemstone.

Brilliance is determined by the cutting and the refractive index of the material. Diamonds have a very high refractive index of 2.41. Diamonds have the potential, if properly cut, to be exceptionally brilliant. However, this is nothing compared to the 2.9 RI of rutile. Not counting synthetics, there are at least 15 minerals with a higher refractive index than diamond!

MYTH: A person can make a lot of money selling diamonds.

As the Internet has continued to proliferate and GIA has established well accepted grading standards for diamonds, margins on cut diamonds have continued to be thin.

MYTH: Diamonds have more “fire” than any other gemstone.

Diamonds are know for their fire, or dispersion. This is the ability to separate white light into the color of the rainbow. Diamond has a dispersion of .044, which is quite high. However, it is a far cry from gems like rutile with a dispersion of .330!

What is a Diamond?

Diamonds are a natural mineral and they are also produced in the laboratory. Lab made diamonds are primarily used as abrasives, but they are beginning to make their way into the jewelry industry. (See “Understanding Gem Synthetics” and “Identification of Synthetic Diamonds” in our Reference Library.)

Gemologically speaking, diamonds are a mineral with a chemical composition of C, (carbon,) that crystallize in the isometric system. (See “How Gems Are Classified” in our Reference Library.)

With a hardness of 10, diamonds are the hardest substance in nature. Harder substances have been created in the laboratory, but they are extremely brittle and have no practical use. If a harder substance is ever found that does not break down so quickly, it will greatly reduce the time need to cut diamonds.

Diamonds have a refractive index of 2.41, which is very high. Being as they form in the isometric system, they do not have any birefringence or pleochroism. They have a specific gravity of 3.51 to 3.53, which is a bit more than average.

Exploring Colored Stones for Engagement Rings

Exploring Colored Stones for Engagement Rings

Jeremy and I are engaged. I've written before about what I think of the diamond industry, and the fact that De Beers has been brainwashing the entire country into believing that

  • Diamonds = Love
  • Diamonds = Committment
  • Diamonds = Forever

I like to think for myself, and I don't buy into the mass thinking that in order to get engaged, you get a diamond. Diamonds aren't even as pretty as other gemstones. Contrary to what De Beers wants you to think they aren't even Rare! Sapphires, Emeralds, and Rubies are all much rarer than diamonds. Whats more, these colored gemstones have a beauty and presence that diamonds can't match.

Emeralds are too soft and fragile to be worn as every day rings, so that takes them out of the running for engagement ring gems that are meant to last a lifetime.

But sapphires and rubies (both in the corundum family) are the second hardest gem (after diamonds). Diamonds are a 10 on the MOHs hardness scale, while sapphires and rubies are a 9. The MOHs scale is not linear, however. And its only based on the definition of hardness as the ability to scratch a softer material, which while helpful, is not the only factor in determining durability. The Mohs scale is a purely ordinal scale, so the differences between each number is not linear or logarithmic. For example, diamond (10) is 4x as hard as corundum (rubies and sapphires, 9), while corundum (9) is 2x as hard as topaz (8). So basically, the Mohs scale can be taken as scale of relative hardness.

Either way, corundum (sapphires and rubies) are hard enough for everyday wear as an engagement ring. They may be somewhat less hard than diamonds, but even diamonds can be chipped and worn down. It is surprisingly not uncommon for people to chip diamonds on the girdle, so getting a diamond does not guarantee that it is "forever."

Due to some excellent advertising, diamonds are believed to be the rarest of gemstones. But if you think about it, all of the women you know probably own at least one diamond. Diamonds are actually not very rare at all, in fact, among gemstones, diamonds are actually the most common.

The mineral corundum is fairly common, but gem quality corundum (sapphires and rubies) is quite rare, consisting of only 1% of all mineral corundum found. The most common is blue sapphire. Many people are not familiar, but sapphires can come in almost every color, including green, yellow, purple, pink, orange, etc. The red colored ones are called rubies. The pinkish orange sapphires are known as padparasha, and are highly prized, as they are only mined in one mine in Sri Lanka, and are very rare.

It may be surprising that blue sapphires are more expensive than say green or yellow sapphires, since green or yellow are more rare. But as with everything, it is not rarity that drives pricing, but demand. The highest demand is for deep blue sapphires, so these are the most prized and most expensive.

Rubies are the red variety of corundum, and are much rarer than the blue ones. Rich reds are the most prized, and a large clear red ruby will fetch a very high price.

My Engagement Ring

Personally, I like colored stones a lot better than diamonds. Colored stones are also typically cheaper than diamonds (but a high quality colored gem will still cost $1-2000 per carat). And getting a colored stone means you avoid being a shill for the diamond industry.

I am a proponent of getting what you like, not what society thinks you should get. If you like diamonds, then get diamonds. But if you like sapphires or rubies, or even topaz or something else, get that instead. You'll save a little bit of money so you can upgrade your setting or save for your future life together.

I will be getting a Sri Lankan blue sapphire that is unheated and untreated. It will be custom cut by the lapidarist Jeff White. I will be updating this blog with pictures of the stone in progress as well as the final result when it is finished. I am planning on setting the sapphire in a platinum solitaire setting. I like the Vatche Royal Crown setting. It is a 6-prong trellis style, which seems very elegant.

The Vatche Royal Crown setting I am considering. Picture this setting with a blue sapphire. 

The Vatche Royal Crown setting I am considering. Picture this setting with a blue sapphire. 

This picture shows the 6 crossed prongs in the trellis setting nicely. 

This picture shows the 6 crossed prongs in the trellis setting nicely. 

Do you have any opinions on sapphires vs diamonds? Which would you choose? And do you have any thoughts on designing my engagement ring?

Colored Gemstones!

Colored Gemstones

The following post is a very helpful reference for purchasing colored stones. The full thread can be found at the pricescope colored stones forum.

First of all welcome to our technicolour world! :wavey:

If you've never bought coloured gemstones before, you're in for a real ride and I'm hoping that this thread may help you on your quest for your "special" one! One thing it's important to know .......... this part of PS is frequented by gemstone lovers from vendors to collectors to enthusiasts to newbies! At the end of the day, we all have opinions/likes/dislikes but ultimately you must buy what you LOVE, not what others tell you to buy! Also, don't chase the "gemstone of the month"! Typically there are trends on this board, Mahenge Spinel for a few months, followed by Spessartite Garnets, then onto Sapphires etc., but running with the pack can be boring. Don't buy because something is flavour of the month - buy because you'll wear and love it!

Believe it or not, jewellers in your neighbourhood (with some exceptions of course) very rarely have the specialised knowledge that you'll find on this forum. If a jeweller hasn't run tests on a gem and says "that's an X stone" then my advice is to take that with a pinch of salt. In order to verify what a stone is you normally have to run a battery of tests - some can be done by jewellers such as testing the RI (Refractive Index) of a stone - sometimes can be done with mounted stones but not always - but some tests really have to be conducted by a laboratory. You wouldn't let somebody tell you you had a blood disease without a blood test would you? It's the same thing!

Why is it different from buying diamonds?

If you buy diamonds - forget everything you've learned! Buying coloured gemstones is a whole different ball game. For example, when you buy diamonds, you can evaluate performance (or get a good idea) by looking at statistics, depth, girdle, table etc and by looking at scans. You can't buy coloured gemstones purely on numbers. In fact, you've already got the tools you need - YOUR EYES! Generally speaking, coloured gemstones are valued by colour first - clarity is not such an issue (more about this later)


So, colour is king! Generally speaking the more vivid a gem appears, the more valuable it is. You will see words like "tone", "hue" and "saturation" used. A table below shows what these mean and I find this visual representation good because it's something I can remember! The table below shows the colour blue but the same is true for other colours! Interestingly, a pure stoplight red is one of the most valuable colours for a gemstone and is very rare. Finding a pure red stone is probably the most difficult search! However, you may prefer lighter tones or less saturated gemstones. If you do that's fine and lucky you because actually that means you'll be paying less! Every cloud has a silver lining!

There's a bit more about this on this link you may find interesting - it's quite basic so not to traumatic to read.


Another word you may see when discussing colour or performance is "extinction". Extinction is basically when a gemstone has lots of "black" areas - when you move the gemstone around some parts will remain black and NOTHING you do will make that change. If a gemstone has been cut so that it has extinction, it'll always have extinction! See the photo below and here's a link that discusses it in great, easily to understand, detail.

Extinction in a gemstone. Note the areas of blackness. 

Extinction in a gemstone. Note the areas of blackness. 

So what's a "window"? Well a window is when a gemstone has been cut (typically) very shallow. What you'll see is a part in the centre of the gemstone that appears to lighten or even lose all of its colour. In effect it's a window and you can see through it! Why's that bad? Well, it means the colour is not being reflected back to your eye so it's negatively impacting on the performance of the gemstone. Small windows can be disguised by using a setting that has a more enclosed basket under the gemstone (in effect it acts as a mirror that helps to reflect the light back to you). But be aware that not all settings will do this and not all windows will close. An example of gemstones with windows is in the photo below.

Windowing in a gemstone. Note the very pale area in the middle of the gem that you can "see through"

Windowing in a gemstone. Note the very pale area in the middle of the gem that you can "see through"

Often I see somebody say "should I buy this and then have it recut"? My advise is always not to unless you (a) really know what you're doing or (b) have been in touch with a cutter who has evaluated the stone and thinks a recut may be possible. This is a skill in itself and not for the faint hearted. If you do recut a stone, please be aware that it may dramatically alter the stones appearance and it may not be for the best! Also bear in mind, some of the most valuable gemstones on earth have been cut to preserve weight and so may be windowed but don't be put off buying them because you could be missing out on a real bargain!

Should I buy a "precision" cut gemstone or a "native" cut one and what's the difference? Well, this is a personal preference. Precision cut gemstones are exactly what they say on the tin and they will be cut to maximise performance. If you will only settle for perfection then this is the route for you! However, precision cut gemstones are a smaller portion of what's available on the market. The majority of coloured gemstones are not cut to precision. You will sometimes see these termed as "native" cut stones. This terminology can sound derogatory but think of it as meaning "not precision". There are native cut stones and then native cut stones! Some are cut so wonkily that you'll need to balance on one leg and tilt you head to one side with one eye closed to make the gemstone look straight! Clearly the value in such a gem will be less than one that is more pleasing to the eye. There are a large number of collectors who don't mind buying native cut stones because there are some quite beautiful ones. The most important thing is that you buy what YOU love and what appeals to you. Precision cut or native cut it doesn't matter!


Inclusions can be a good thing (believe it or not)! They can sometimes verify that you've got a natural gemstone and not a synthetic or lab created gem. However, there's a difference between a few inclusions and then inclusions that take over the whole stone and affect the overall beauty! "silk" is a really good example of this. Some gemstones have rutile type inclusions that make the gem look silky or hazy. It can, in some gems, make them glow incredibly! In other cases it can make a gem look murky and in need of a good clean! Unfortunately, you can't clean out internal inclusions so don't make the mistake of buying and thinking a good rub with a cloth will sort it out - it won't! Inclusions can be fascinating or they can be incredibly annoying. Again, judge what's acceptable to you.

Very few gemstones are flawless. In fact, gemstones are often listed as "types". Some gemstones are type 1, some type 2 etc. The type refers to whether they are naturally included or not. This website has a list of gemstones and what category they fall into. It's important you read this so you know what's "typical" for your chosen gem.


Surprisingly, not all gemstones are suitable for every day wear. The only ones that are considered durable enough are diamond, ruby, sapphire, alexandrite, chyrsoberyl and spinel. Most others, for one reason or another, are more prone to damage by frequent wear. Durability is not just about hardness but it's about the chemical make up of the gemstone i.e. the cleavage. If you knock some gemstones in the right place, you can split them completely in half - a bonus is you'll have a pair of earrings but it may be an expensive accident.

Make sure you research the gemstone you love. If it's lower down the MOHS scale then it's less durable and more prone to scratching, chipping and pitting. Generally, don't get gemstones near water, don't do the gardening in them, think before you change a tyre on your car and know how to clean them properly! However, if you know how to take care of your chosen gemstone then don't be frightened to buy what you like. There are many examples of people who have worn Emeralds (a softer, more brittle stone than a sapphire) for years without a problem and then others who have one for 6 months and have damaged it beyond repair.

Carat weight/Size

Is weight important? Well carat weight can certainly be important. For most gemstones, over 1ct is good. For rare gemstones such as Paraiba Tourmaline, Alexandrite, natural Rubies etc., the size of the gemstone can be phenomenally important. In more easily obtainable gemstones it's a nice to have!

Now then, we come to THE most important thing for you to know about when buying coloured gemstones! TREATMENTS!


If you buy a Rolls Royce you expect a Rolls Royce don't you? You'd be really fed up if you found that you'd bought a Skoda in a Rolls Royce wrapping wouldn't you AND you'd paid Rolls Royce prices? Well, that's why treatments are important for you to understand. Again, this is personal. Some will accept only natural gemstones, others will accept some but not all treatments, others just don't care and want a sparkly gemstone! Who's right? Everybody! It's a personal thing again! You need to do your own research because treatments affect buying prices and values of gemstones so it's probably the key thing to deciding if you've paid a fair price.

I can't cover all treatments here but here's a few and you can always do internet searches for more information if you want to research in more detail. BE AWARE, NOT ALL TREATMENTS ARE DISCLOSED! YOU MUST ASK AND THEN VERIFY WITH A LAB REPORT IF YOU'RE BUYING AN EXPENSIVE GEMSTONE:-

Natural and untreated - gemstones are mined, cut and sold exactly as nature intended them to be! They are exactly as it says on the tin - natural. They are usually the most expensive type of gemstone and most difficult to find. Some gemstones are never or very rarely treated and so this is expected. Research your chosen gemstone to see if yours is one that is normally left alone!

Heated - Some gemstones are heated in the Earth naturally and it affects their colour, changing them from one colour to another. For example, Tanzanite is naturally a brown muddy looking gem but some, heated by the earth, comes out of the ground in a beautiful blue or purple, green or orange etc. Some gemstones are heated routinely and this is accepted. So, for example, if Tanzanite comes out of the ground brown, it's heated by man and becomes a gorgeous blue. 90% of all Tanzanite is heated in this way so it doesn't affect the price. Other gemstones like Ruby for example, is heated to improve appearance by lightening and making inclusions less visible. A heated gemstone (with the exception of gems that are nearly always heated) will be expensive but not as expensive as a natural untreated gemstone.

Oiling - Most commonly you see this term used when discussing Emeralds. Oiling goes back to Egyptian times and it's a way of infusing inclusions in Emeralds ("jardin") with an oil to make them less visible and the gem more beautiful. There are different types of oils and if you buy an Emerald in particular it's useful to know what oil or treatment has been applied because oil can dry out and make need to be re-done.

Now we come onto those treatments that are a bit more contraversial!

Fracture filling/Dyeing - Some gemstones have their inclusions filled. This treatment is not necessarily stable and putting a gemstone into a sonic cleaner can cause the gemstone to spit out the treatment leaving you with a very very ugly gemstone. Rubies and sapphires are often filled with glass, lead, and are even sometimes dyed. Is this acceptable? Well, again it's personal preference. This does affect the value/worth of the gem and therefore if you buy a gem that's been treated in this way, please make sure that you're not paying too much.

Irradiation - Some gemstones are irradiated to improve/change colour or appearance. For some it affects value (for example a coloured diamond) for others it doesn't i.e. some tourmalines are irradiated. Leaving aside coloured diamonds for a minute, in some cases this treatment isn't detectable but it is stable.

Beryllium or Lattice Diffusion - Years ago, it was discovered that adding an element into the heating process with the gemstones could actually change the colour of the gem to make it far more pleasing to look at. When this process first hit the market it only covered the surface of the gemstone so if you chipped the stone, you would see a different colour underneath! Technology has moved on and now diffusion goes right through the gemstone so even if it were to be cut, you'd see the same colour throughout. Is this a natural gemstone? Well, yes but it's a natural gemstone that has been artificially changed by man so that it's more acceptable. Typically these stones don't have much value but can look very beautiful. If you're looking for a cheap sapphire (for example) then some of the loveliest most affordable colours are diffused. Please be aware that these will not be heirloom pieces and so you shouldn't pay much for these.

Coatings - Gemstones like Topaz are commonly coated. You can find some diamonds that have been coated also. The problem with coatings are that if you scratch the gem, the coating will come off. It's not too much of a problem if you've bought an inexpensive topaz but imagine if you've bought a pink diamond thinking it's natural, scratch it and then off comes the colour!? Not good.

Verifying what you've bought

Unfortunately there are quite a few gem sellers who will not disclose treatments and this means that you could buy a gemstone for a high price when it's actually worth less. This forum has a section that has vendors commonly used by frequent posters on this board and they're named on there because they are honest sellers (some of whom frequent this board) so if you're really worried then look at what they have to offer before venturing into the world of sharks that is Ebay!

For coloured gemstones, lab reports are valuable because they will verify that you have (a) bought the gemstone you thought you were buying and not a synthetic (b) the size (c) sometimes colour will be graded (d) location if it can be proved and if you've asked for that to be included. What a lab report won't do is put a value on your gemstone. Generally speaking if you're in the US, AGL is the lab to go to for coloured gemstones. In Europe it's either Gubelin, GRS or AIGS.

So, do some research but remember, buy what you like and what's right for you might not be right for the next person but will be loved by others! Happy gemstone buying!

I'm sure I've missed some key points so follow posters, please jump in and add info!