DIAMONDS - A gemology course on diamonds & grading

DIAMONDS Gemology course on gemstones & diamond grading. By Charles Merrell Only about 19% of all diamonds mined in the world are good enough to use in jewelry. How is a diamond cut: A rough or raw diamond (below) is Octahedral or 8 sided The last diagram on the right shows how a rough diamond 4 C's: Cut, Color, Carat Weight & Clarity. Plus the 5th C . . . . . . COST Cut Round, Oval, Emerald, Marquise, Pear are the standard shapes & often called the “cut” but don't confuse diamond "cut" with "shape." When a diamond gemologist says "cut," that's a reference to how well the diamond is cut to enhance its reflective qualities; it refers to how well proportioned the diamond is. An ideal cut reflects the light back up giving a diamond it's brilliance. The different parts of a diamond European Cut Diamond: Note the cut culet that results in the image of a “hole” at center Color Grading color begins with D, E, F (colorless) G, H, I, J (near colorless) then on through L, M, N and continues all the way to Z. When jewelers or gemologists refer to color, they mean the presence or absence of color in a diamond. Color is a result of the composition of the diamond and under normal conditions this never changes over time. A colorless diamond is like a clear window: it allows more light to pass through it than a colored diamond. Colorless and near colorless diamonds emit more sparkle and fire. The formation process of a diamond ensures that only a few, rare diamonds are truly colorless. Thus the whiter a diamond's color, the greater its value. Carat Weight Carat refers to how much a diamond weighs. According to many sources, the term carat comes from the Greek word meaning “fruit of the carob tree.” In ancient times, the seeds of the carob pod were used as standards for weight measurements, since the size of their seeds were almost always identical. This provided a natural standard of measurement. In 1907, at the 4th General Conference on Weights and Measures, it was agreed that a modern diamond carat should equal precisely 200 milligrams. This is technically known as a metric carat. It's the standard diamond weight that is used universally today. Also 1 carat is equal to 100 points. A one point diamond is slightly larger that a period at the end of a typed sentence. A 1.50 Carat (Ct.) diamond is 150 points. Clarity Most diamonds contain inner flaws or inclusions that occur naturally. They are part of Mother Nature's imperfection. It used to be one way to tell if a diamond was real. These flaws give a diamond its distinctive beauty and make each a stone unique. They are identifyable, much like fingerprints – no two diamonds are alike. The visibility, number and size of these inclusions determine what is called the clarity. IF – Internally Flawless – Perfect clarity - no inclusions whatsoever VVS – Very Very Slight Inclusions - Tiny microscopic pinpoints of inclusions. Only visible under microscope & nearly invisible under 10x powered loupe VS– Very Slight Inclusions – Just barely visible pinpoints of inclusions. Visible with 10x powered loupe, almost always invisible to the naked eye SI – Slightly Included - Visible with 10X powered loupe and most are not visible to the naked eye. I - Included – inclusions are from barely visible to very visible to the naked eye. GRADING Diamond grading can be very subjective – some comparing it to being sick and going to 3 different doctors; getting 2 -3 different opinons. There have been instances of a diamond being graded slightly different from the same grading lab. It's best to visually look at a diamond without a 10 X loupe and then with a loupe. Regardless of grade, it's important how the stone looks, especially in plain daylight NOT under jewelry store diamond lights ! You want to see how the diamond “faces up” - it's sparkle or brilliance. Basically how it looks visually. The same grade can have more or less flaws. One large one versus several pinpoint ones. It's better to stay away from black inclusions; white to opaque is much better. See 3rd picture for an example of a white inclusion - sometimes called a "feather" An average VS diamond VS (very slight inclusions) diamond above with carbon inclusions lower & center plus 2 smaller ones upper right. The next 2 photos show examples of SI diamonds and the vast difference within a grade. This same difference can be seen in all grades. The SI (slight inclusions) diamond above with cluster of carbon inclusions and 2 smaller ones. Even these would not be visible to the naked eye. This diamond would be more desirable than the one below – even though both would have the same grade of SI. This SI diamond above with 1 major and 2 minor black carbon inclusions plus 1 white inclusion (sometimes called a "feather") marked with a green arrow. The same grade can vary in type of and severity of inclusions. In the above case the diamond's major inclusion (left red arrow) would be visible to the naked eye, making it less desirable as well as lowering it's value. There are other factors that affect the quality and thus the value of a stone but these are somewhat lesser in importance than those mentioned above. Other factors: Other things that affect a stone's value to some degree, although much less than Cut, Clarity and Color include Fluorescence, Polish and Proportion or Symmetry. These are defined as follows: Diamond Fluorescence This refers to how a diamond responds when subjected to ultra-violet light. UV light is what makes your whites look whiter, your teeth bright white, and your black-light posters glow. Some diamonds, when they are exposed to UV light, glow different colors . Primarily they fluoresce blue – in fact about 98% of the time, the glow is blue in color. On some rare occasions a diamond can glow white, yellow, green, or even red in color. Diamonds with strong to very strong fluorescent can appear hazy at times in regular light. Polish - merely means how polished the facets are. Proportion Or Symmetry Most gemologists agree that the best cut diamonds follow a set of formula calculated to maximize brilliance. This is seen in a diamond's proportions. Symmetry refers to how well aligned the facets of a diamond are. Some imperfect examples are shown on the next page. These are the major examples of poor proportion, symmetry. These are not that big of a factor in modern day cut stones. Not nearly as they were 75 -80 years ago. This due primarily to modern technology in the cutting process. These can be found in older cut stones or in pieces of antique jewelry. However, many of the larger, older stones were recut over the years. Examples of poor proportion or symmetry Of primary importance when buying a diamond for jewelry: Two things when buying a diamond; you should first determine if a diamond is clean to the naked eye and if it has suitable brilliance. Does it look good.....does it have “fire”. Is there a visible “wow” factor ? Next use a loupe but don't get hung up on minor flaws. If it’s any cleaner than eye clean, it’s just going to cost you a lot more money without giving you anything more in return. Rarely, if ever, will you use a loupe again to look at that diamond. As a piece of jewelry, it is meant to bring happiness and a smile to the one wearing it. Charles Merrell With more than 40 years experience in gemology, jewelry design & personal property appraisals, Charles Merrell has lectured on diamonds & semi precious gems as well as appraisal & restoration techniques. The above lecture is taken from courses Charles taught on gemology & diamond grading. Professional experience: Mar, 1980 - Present Independent personal property & jewelry appraiser, fine art & auction consultant Feb, 1980 - Aug , 2000 Chas. Merrell, Inc. Fine Jewelry, Antiques & Appraisals 115 Metairie Road Metairie, LA 70005 Jan, 1976 - May, 1980 Self employed – specialized in antiques, jewelry & rare coins. Prepared personal property & jewelry appraisals; gem identifications. Consultant - jewelry & antique restoration. Jan, 1971 - Dec, 1975 Maison Blanche - Rare Coins & Jewelry - Ass’t. Manager Gulf States Rare Coins & Antiques - Manager & Chief Appraiser Additional Projects & Studies: March, 1995 University of New Orleans, New Orleans, La Guest lecturer, subject: “Natural flaws in Diamonds & Sapphires - Determining Genuine or Synthetic” April - July, 1990 Restored & repaired Faberge’ necklace for New Orleans Museum of Art. Restored enameled Faberge’ pieces for a private collector. March - June, 1985 Restored & re-gilded Monstrance for St Anthony of Padua Church, New Orleans, La. Appraisal & repair of antique Russian silver pieces for Gates of Prayer Synagogue, La. 1984 - 1996 Consultant - restoration work on crown & scepter for School of Design - Krewe of Rex Organization, New Orleans, La.