AboutThomas Expertise Have a question about jewelry repair or working with gold or silver jewelry and gemstones? I am a working professional bench jeweler, involved everyday with setting stones in mountings, designing and making jewelry, repairing and some custom manufacture. Over 30 years experience. If you work with jewelry as a hobby or as a profession, I might be able to help. I deal with the retail business, not mass production. Ask privately if you wish. See the box for that: It keeps your question between us. Please DO NOT ask MAKER'S MARKS, but metal quality marks are fine to ask. Please DO NOT ask diamond prices. See a gemologist for that.
Experience Education is English/Physics!Started in human resources, to advertising, to jewelry...wow, what a road. Now a jeweler for many years. I have had formal training in jewelry work and many shared experiences with top grade jewelers. We just never know were we will go or be. Follow your best, your dreams, with some discretion!
Expert: Thomas Date: 1/2/2006 Subject: gemstone idendification
Question Dear Thomas,
Before I place my question, I wish you happy new year.
I send this message to you because, from what I saw in the website, you give the most understanding and detailed answers.
I have a question that might sound stupid but...
How can anyone, who is not an expert, idendify a diamond from other colorless stones, such as white sapphire or even a Cubic Zirconia. The question of course applies also for colored diamods and it's difference from other colored precious stones (such as topaz etc).
For your information I found the website in Google search engine.
I thank you in advance.
Best regards
George
P.S
I would like to buy some books about Gemology and I would like you to give me a couple of choices if possible.
Answer Good Evening George and thank you for this question.
Since you would like a recommendation on gemology books, I believe you understand my answer will only touch the surface of gem identification. Books, books and more books are published on the subject, some covering general information and others so specific as to only be concerned with the “inclusions” in gemstones, etc. At the end of this answer, I will recommend a few books which should be useful. You should also know that my gemology skills are a bit out of practice, having put my work emphasis on jewelry design for several years. Still, I should be able to answer this question in a satisfactory manner. Your question is not stupid at all. You need an answer and that is enough for me. : )
There is no way I can adequately cover diamond identification in one answer. However, I will provide basic tips and directions to pursue. Let it suffice as true that experience is the best means of “ knowing a gem is or is not a diamond”. Years of experience with diamonds gives a jeweler a “feel” and “eye” for a diamond. Sure, in most cases it is fairly easy for a person who has examined and handled hundreds of diamonds to say with fair certainly, “This is a diamond and that stone is not.” Appraisal is a different matter since comparison is made among grades of diamonds, diamond judged against diamond grading methods. With larger marketable man-made diamonds possibly coming on the scene before long, the jeweler will need to bone up on the characteristics of natural and the lab grown diamonds. A jeweler must also be aware of natural fancy colored diamonds and how those compare to natural stones colored by irradiation and heat. All of that is another subject. Let's move on to more basic tips in diamond identification.
One thought to keep: Much gem identification is an elimination process. It is often easier to tell “what a stone is not” than to prove what the stone is. The tips provided follow that idea.
FIRST VIEWS OF A GEMSTONE. You need a clean stone to start. If mounted in jewelry, all should be cleaned thoroughly. Cleanliness allows a good look at the gem. You need a loupe, a jeweler's loupe magnifier. The loupe should be 10x. When you look at a stone with a loop, hold the lens next to the eye and bring the stone to the lens. I will hold the loupe in one hand, right at my eye, with a finger of that hand extended toward the front of the lens. Bring the stone up to the lens, using the extended finger for guidance and support. To hold the loupe away from the eye and near the stone will not work and will “blow your cover”, revealed as someone who has not used a loupe before.
Knowing how to use the loupe is handy when visiting a jewelry store. That sort of visit will be helpful to you in learning more about diamond identification and the lens is vital. You need to be around diamonds to see the characteristics I will mention. Unless you personally have a pile of these stones, a few visits to jewelry stores could help a lot. You might ask a clerk, “How can I tell this is a diamond?” Some clerks will give blank stares and look at the ticket on the item…it says diamond. Others will bring out a lens or a microscope for you to use, with explanation of what to see.
BASIC TIPS.
First, look at diamonds. You will see a shine, color reflections and sparkle not seen in other gemstones. A colored gem like aquamarine or even sapphire does not have the radiance of a diamond. Those gems do not have the “dispersion” of a diamond. Dispersion is the ability of the stone to break light into colors, like a prism. Though a very bright and lively sapphire will have wonderful reflections of color, it will not show the “other colors” seen in a diamond rotated under a light. Dispersion is one characteristic to notice.
DISPERSION. Some man-made diamond substitutes have great dispersion of light. Examples are the older simulated diamonds like natural zircon, synthetic rutile and more recently moissanite. These stones might fool the casual eye. Compared to a diamond, natural zircon looks different for a reason mentioned below. Compared to diamond, synthetic rutile is much, much too colorful, almost looking artificial. Moissanite will look much like a diamond but as with zircon, there is a definite difference. CZ, a man-made form of zircona related to zircon in chemical makeup but different in crystal shape simply does not have the dispersion shown in a diamond. The difference is obvious when side by side and moved under light. Also, a little smudge of dirt on the back of a CZ will cut down the reflections of light from the stone considerably. A diamond dirty on the back side(pavilion) will generally still be very reflective is the top of the stone is clean.
Most colored gems will not show the dispersion of light shown by a diamond. A green diamond will look nothing like a green emerald. A blue diamond will look nothing like a blue sapphire and certainly not like a blue topaz.
Note. I do not recommend any particular website sellers. I pick these at random considering the info presented.
REFRACTION. Refraction is one of the characteristics showing the difference in a diamond and some close substitutes, like natural zircon and the new lab grown moissanite. A diamond is singly refractive. What does that mean? Lets look at zircon and moissanite which are doubly refractive. Stones with double refraction handle light differently than singly refractive stones. Refraction is like looking into a pool of water, seeing a fishing line and noticing how the water affects the light and the angle of the line is different in the water than in the air above the water. The light is bent. With a doubly refractive gemstone, you might see “two” fishing lines, close together but two, indeed. A loupe and a look down inside a natural zircon or a moissanite will show the difference. Look into the stone, holding all steady with focus on one of the facets (face) cut on the bottom of the stone. Look in from the table or top facet on the stone, down and into the gem. See where the facets(mirror like faces) come together? This is the line where one facet meets another and is called a “meet” by stone cutters. Doubly refractive gems will show a slight fuzziness of that line or even show a “two line” image instead of one. The light is bent differently and two lines or a fuzzy one shows when in fact there is just one line where the facets come together. Diamond is singly refractive and does not do this. Any gem showing double refraction is not a diamond! We might not know what it is but it is not a diamond. CZ or cubic zirconia is not the same as natural zircon. The basic chemical make up is the same but the crystal form is different. That crystal form is cubic as in diamonds and is not doubly refractive. While a natural zircon shows the doubled facet junctions, a CZ does not.
POLISH. Polish is another characteristic of diamonds most often lacked by other gemstones. Take that CZ stone and look for double refraction…humm..none there. What is this stone? Look at the surface of the stone, at the polish of the facets and especially where the facets come together, the meets. This is the line between the facet faces. On a diamond the line is quite sharp and focus is difficult sometimes. With a CZ, you will see the line and notice a slight rounded surface, like someone had a nice sharp edge and sanded it to be slightly rounded. The rounded junction of the facets is a dead giveaway that you are not dealing with a diamond…what the stone is I cannot say but it is not a diamond. Another home test is to focus your eyes on the stone table, the large flat facet face on the top of the stone. Refocus to see reflections of something around you, using the table facet like a mirror. With a diamond, the reflection is generally precise and uniform. With many other stones which do not “accept” the fine polish of a diamond, the reflection may be blurred or distorted. Unfortunately, much of the reflection information you see is a bit subjective.
SPECIFIC GRAVITY. Weight or more accurately “specific gravity” is one more simple test. You need a very delicate scale to do this testing and a chart to show approximate diamond weights for certain sized diamonds. With CZ the chart is not needed since most are sold in what is called “diamond sizes”. Order a 1 carat diamond size CZ and you get a CZ with the same diameter as a 1 carat diamond. The weight is different, yes it is, and carat is a weight, not a dimension. A carat is 1/5 of a gram, a weight. Maybe I can clarify that a bit and speak of Specific Gravity.
For example, if someone gives you a pound of feathers and a pound of lead then asks you to box up the stuff. Don't compress the feathers, let that fill the box. Obviously, both boxes carry the same weight. But, the pound of feathers needs a much larger box than the pound of lead. Lead is more dense than feathers. This is another way of saying the specific gravity of lead is greater. Gemstones have a density or specific gravity characteristic of the stone.
For diamonds, the sg is 3.52. This means a diamond has a mass of 3.52 compared to an equal volume of water. Science types will say mass, mass, mass…which it actually is but we simply make it simple and call it “weight”. A cubic zirconia has an sg of about 5.7, meaning it is denser and “heavier” than diamond. A one carat diamond weighs 1 carat, 1/5 of a gram. A CZ cut to the same size as a 1 carat diamond weighs more since it is a denser material. In fact, the CZ will weigh about 1.62 carats on an accurate scale. (I got that by dividing 5.7 by 3.52.) If you have loose stones, compare the weights to that of an equally sized diamond. Any large difference tells you something is amiss and the stone is not a diamond. Stone proportions are important, too, but this simple method will put the diamonds on one side and the CZ stones on the other rather quickly. If you have an accurate scale, you can weigh in grams as well as carats but need to be able to get down to low numbers to be accurate. Remember, one carat is only 1/5 of a gram.
I could go into inclusions, internal flaws, girdle edge polishes and more. This answer cannot be that long or that specific. What I have provided is a few basic and simple tests, provided you have the means to do the testing. For more, I do recommend books with images and more specific “how to” information on gem identification. As for colored gems besides diamonds, the simple tests above will distinguish most of those from diamonds. You still need a good look at diamonds to make the message clear.
Suppliers. This is one company selling loupes. www.contenti.com
Search jewelry loupe to find others or check to see if a local hobby store or jeweler can get you a good loupe with corrected lenses.
Books. I provide one website of a long established supplier to the industry. On the following page you will see several books. The next two links are to those books descriptions. Either is a good start. Local book sellers may be able to get the books for you. You might search seller sites to see what is out there and read descriptions. Some books are quite good and others are simply too simple. Look for ones with info on tools and methods needed for gem id as well as comprehensive coverage of gemstones. Do not get an advanced book for the practicing gemologist. These will assume you have the equipment already.
One last hint: Gemstones are cut from crystals, minerals formed is specific patterns. Crysatalline materials will feel cooler to the touch than will glass, which is not crystal in structure.
George, that is the answer. This was not a stupid question. I wish more would ask such questions. Agreed, the answer leaves more to ask and learn and only gives a slight touch on the methods and expertise needed for stone id's, including diamonds. The basic stuff I have given will help in basic separation of diamonds from most other gemstones.
God Bless and best wishes for this new year. Thomas. 01/02/2006 9:22 PM
