The word gem is derived from the Latin form of gemma, meaning flower.

The word gem is derived from the Latin form of gemma, meaning flower. The love of precious stones is deeply implanted in the human heart. All the fair colours of flowers and foliage, the blue of the sky and the glory of the sunset last only for a short time. In a world of change, the permanence of coloured gems holds a charm all its own. From the earliest times in man s history, precious gems have been held in great esteem. They have been found in the monuments of prehistoric peoples, in the tombs of the Pharaohs, the civilizations of the Incas and the Montezumas. More than their intrinsic wealth or as personal adornment, these gems were deeply significant talismans with profound and magical abilities to protect the wearer from harm or bestow a multitude of virtues. Romancing the Stone has been a part of human culture for centuries. What is a Gemstone? A gemstone is a mineral, rock, organic or petrified material that when cut and polished is collectible or can be used in jewellery. Most gems we encounter are mineral and these are classed according to their crystal habit. Mineral specimens ( Crystals ) are very often strikingly beautiful in their untouched natural state and the art of the faceter finishes the crystal into the beautiful gemstones with which we are most familiar. GEMSTONES 1 &2 will explore only a portion of the vast array of coloured stones that exist today, and will focus on those gems that are or may be presented in our showcases. The learner will understand the many permutations and natural conditions that make certain gemstones valuable, their endless diversity, desirability and how to talk about these very precious jewels. EMERALD CRYSTAL EMBEDDED IN CALCITE. THIS BEAUTIFUL RHODOCHROSITE SPECIMEN WILL NEVER BE A MAINSTREAM JEWEL. THIS IS A VERY SOFT GEM THAT IS QUITE RARE. There are several basic value factors that need to be understood about coloured gemstones and these are also the reasons why they hold our fascination. Gemstones that have been most successful over time are those which have a certain degree of rarity. They cannot be so rare that no one has ever heard of them, such as benitoite which is not really available or too common like rock crystal quartz which in turn, affects their desirability. The gemstone must endure a certain amount of wear to be enjoyed, and the durability and stability of any gem is a key factor. And of course, the gem must have beauty. Gems are classified into different groups, species and varieties. For example ruby is the red variety and sapphire the blue variety both belonging to the species corundum. Emerald, aquamarine, heliodor and morganite are all varieties of the species beryl. Many gem species are quite diverse, some with named varieties or merely classed by their hue description. THE GEM WORLD IS SO DIVERSE THERE IS A GEMSTONE HUE AND PRICE POINT TO SUIT ANY TASTE AND BUDGET!

There are more than 1500 different coloured gemstones that may be fashioned into jewellery. Listed here are those gems that we will possibly encounter in our showcases. PRECIOUS VS SEMI-PRECIOUS: JUST SAY GEM! SEMI-PRECIOUS IS AN OUTDATED AND INACCURATE TERM THAT SUGGESTS A TWO-TIER RANKING EXISTS IN THE GEM KINGDOM: THE EXALTED STATUS OF PRECIOUS AND AN INFERIOR CATEGORY OF SEMI- PRECIOUS. TALK ABOUT QUALITY DIFFERENCES, RELATIVE RARITY, PRICE RANGES, VARIETY OF HUES AND PRESENT EVERYTHING POSITIVELY. FROM AMETHYST BEADS TO STAR RUBIES, STICK WITH THE TERMS GEM AND GEMSTONE. What causes colour in gemstones? A gem's color is produced when light passes through it. Some colors of the spectrum are absorbed within the crystal structure. Those that emerge combine to give the gem its color. If all the light emerges it will be colorless. CORUNDUM BERYL CHRYSOBERYL QUARTZ SPINEL TOPAZ GARNET ZIRCON TOURMALINE TURQUOISE PERIDOT OPAL JADE SPODUMENE ZOISITE RUBY STAR RUBY SAPPHIRE STAR SAPPHIRE FANCY SAPPHIRE (any other hue except blue) PADPARADSCHA (pinkish-yellow) EMERALD AQUAMARINE MORGANITE (pink) HELIODOR (yellows) ALEXANDRITE GREEN/YELLOW /BROWN HUES CATSEYE AMETHYST CITRINE AMETRINE SMOKEY QUARTZ CHALCEDONY (opaque & translucent, many hues) BLUE, RED, PINK, VIOLET HUES BLUE (*irradiated) PINK YELLOWS, BROWNS ( Imperial ) PYROPE (dark red) ALMANDITE (purplish-red to red) RHODOLITE (violetish-red) SPESSARTITE (orange-red) TSAVORITE (green) MALAYA (browns, orange-browns) BLUE, COLORLESS RUBELLITE (reds) CHROME ( emerald-like green) BI-COLOUR (several hues in 1 gem) INDICOLITE (blues) PARAIBA ( electric blue) Note: Tourmaline occurs in every hue! WHITE BASE CRYSTAL & SEMI-CRYSTAL BLACK OPAL (& SEMI-BLACK) FIRE OPAL BOULDER OPAL JELLY OPAL NEPHRITE JADEITE KUNZITE (pink, mauve) HIDDENITE (green) TANZANITE Minerals, including gemstones, are rated and ranked according to their hardness. While hardness is generally associated with durability, the ability to resist breakage is better described as toughness. When referring to gemstones, hardness more accurately means the stone's ability to resist abrasion and scratching. The most common measure of a gemstone's degree of hardness is based on the Mohs Scale. Devised by German mineralogist Friedrich Mohs, the Mohs Scale rates minerals comparatively from 1 (very soft) to 10 (very hard). What the scale means is that a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower hardness rating. For example, rubies and sapphires, which are composed of the mineral corundum and have a Mohs rating of 9, will scratch each other, as well as topaz (rating 8) and quartz (rating 7). But they will not scratch diamond, which is rated 10. MOHS SCALE OF HARDNESS 1 TALC 2 GYPSUM, PEARL, AMBER 3 CALCITE, CORAL 4 FLUORITE 5 APATITE, OPAL, LAPIS LAZULI 6 FELDSPAR, TURQUOISE 6.5 GARNET, ZIRCON, PERIDOT, JADEITE, ZOISITE 7 QUARTZ 7.5 BERYL, TOURMALINE, 8 TOPAZ, SPINEL 8.5 CHRYSOBERYL 9 CORUNDUM (RUBY AND SAPPHIRE) 10 DIAMOND What the scale does not make obvious is that the numeric values assigned to each interval of hardness are not equal. Some stones are disproportionately harder than others: 10 DIAMOND: APPROXIMATELY 90 TIMES HARDER THAN CORUNDUM 9 RUBY/SAPPHIRE (CORUNDUM) APPROXIMATELY 5 TIMES HARDER THAN TOPAZ 8 TOPAZ: LITTLE DIFFERENCE BETWEEN TOPAZ AND QUARTZ 7 QUARTZ (GEMS WITH A HARDNESS RATING LOWER THAN 7 WILL SCRATCH FAIRLY EASILY).

DESCRIBING COLOUR IS OFTEN A PERSONAL INTERPRETATION. GRASS GREEN AND PERIWINKLE BLUE WILL ALWAYS ADD CHARM TO YOUR PRESENTATIONS. HOWEVER, CURRENT ACCEPTED JEWELLERY TERMINOLOGY IS ILLUSTRATED IN THESE SAMPLES. ORANGE-RED HUE, STRONG SATURATION MED. TONE BLUISH GREEN HUE, SLIGHTLY STRONG SATURATION MEDIUM TONE LIGHT GREEN HUE, WEAK SATURATION LIGHT TONE Considering the near endless variety and desirability of colored gems, it s probably not surprising that color accounts for 50% of their value. Yet until the early 20th century, there was no generally accepted way of describing colors precisely. Then Albert H. Munsell, an American painter and art instructor, brought order to the world of color by identifying three basic qualities or dimensions of color: hue, saturation and tone. Any color can be described by naming these three qualities and these three factors apply to quality judgment of all coloured stones. Hue, Saturation and Tone form the foundation to understand how and why many gemstones can be more rare than others, and allow a universal method to describe coloured gems, both written and verbal. Hue means the specific spectral location of a given sensation of color. The GIA Colored Stone Grading System specifies 31 hues, such as violet, violetish blue, slightly violetishblue, blue, and so on. Saturation is the degree to which a color departs from a neutral (gray) sensation. It can be thought of as the relative purity and intensity of a given hue. Tone is the lightness or darkness of a color. The tone scale is divided into 11 grades, 0 to 10, with 10 being black. Lighting affects gemstone color. The whitest, most neutral light is at midday. Besides adding the least amount of color, this light makes it easier to see the various nuances of color. Gemstone color is judged best under a daylight equivalent. Hue Saturation Tone THIS 3 D COLOUR WHEEL ILLUSTRATES RECOGNIZABLE HUES, NOTICE THE RED HUE RANGE AND THE ADJACENTS HUES MODIFIED BY YELLOWS TO THE RIGHT AND BLUES TO THE LEFT. DESCRIBING HUE IS EASY WHEN YOU PICTURE THE 3D COLOUR WHEEL AND INTERPRETING A GREENISH-BLUE HUE VERSUS A VIOLETISH-BLUE HUE IS EASIER TO COMMUNICATE. YELLOWISH-GREEN HUE, MODERATE SATURATION DARK TONE BLUISH-GREEN HUE WEAK SATURATION LIGHT TONE Incandescent light bulbs may add red, fluorescent lights tend to strengthen blue colors and warm white tubes add yellow. Light under an overcast sky or in the shade may also affect the appearance of colour sensations. Each gem species or variety carries its own potential for best colour, depending on its natural colour range. The slightest variation in hue saturation and tone can make a tremendous difference in price. However, the individual s preference to a particular hue or gemstone is often the deciding factor! HOW TO CORRECTLY DESCRIBE GEMSTONE COLOUR: The hue description is stated first, then saturation strength as variables of weak, moderate, strong to vivid then tone as variables of light, medium to dark. Once these concepts are understood, their application will vary. Some gemstones are exceedingly rare in vivid saturations and some only occur in very pale shades. As an example, over dark tone sapphires are far more common and the value increases exponentially when a sapphire is the most desirable violetish-blue hue with vivid saturation and of optimum tone (usually a middle range) Hue, Saturation & Tone in combination are best used to describe transparent and semitransparent coloured gemstones. Opals, jadeite, pearls and various no-transparent gems are described using different terms.

LUSTER is the amount of light reflected from its surface. Most gemstones have a glass-like (vitreous) luster. Luster is also described as dull, greasy, adamantine or metallic. REFRACTIVE INDEX (R.I): is the amount that light rays are bent by a gemstone, and this is measured using a refractometer. Gems with a high R.I. are zircon, diamond and some garnet varieties. DISPERSION is a gemstone's ability to split white light into the colors of the spectrum. Some highly dispersive gems are demantoid garnet and zircon. DOUBLE & SINGLE REFRACTION is the separation of light passing through a substance into two rays. This occurs in most transparent gems although some like garnet and spinel do not split a ray of light into two and these are singly refractive. PLEOCHROISM is due to double refraction where the light is divided into two paths. This divided light follows different paths within the stone, travel at different speeds and when they leave the gemstone they have different colors. This is a very subtle effect and tanzanite is a good example that shows violet and blue hues together in the same stone. Two colors or shades and are called dichroic, some show three and are trichroic. Gems are sometimes cut in such a way to either to display pleochroism or to hide it, depending on the colors and their attractiveness. SPECIFIC GRAVITY is a variable property among gemstones and is the ratio of the weight of a gemstone to that of an equal volume of water. This is related as a numeric reading of the gems density. For instance, a 5 carat emerald (s.g. 2.72) will have greater mass compared to a 5 carat ruby (s.g. 4.00) of the same weight and proportions. THESE ARE CHATOYANT TOURMALINES. QUARTZ, MOONSTONE, SOME BERYL AND TOPAZ MAY ALSO EXHIBIT CHATOYANCY. PLAY OF COLOUR IN OPALS CAN VARY A GREAT DEAL, AND ARE INCREASINGLY VALUABLE WHEN THE FULLSPECTRUM IS VISIBLE. OPALS CAN BE PREDOMINANTLY SINGLE OR MORE THAN ONE HUE. ASTERISM IS MOSTLY SEEN IN RUBY AND SAPPHIRE, ALTHOUGH SOME BERYL AND QUARTZ VARIETIES MAY SHOW A FOUR RAY STAR EFFECT. TOP QUALITY STONES SHOULD HAVE ALL RAYS BRIGHT DISTINCT AND WELL CENTERED UNDER A SINGLE LIGHT SOURCE. PHENOMENAL GEMS display unusual optical effects. Chatoyancy is bands of light on certain stones and those gems that exhibit this effect have a multitude of minute needle-like inclusions that lie parallel to one another like threads on a spool. Light reflects from the needles, creates a silky sheen. Asterism is when the needle-like inclusions forming chatoyant bands, cross in the centre of a cabochon, creating a 4 or 6 ray star effect. Play of colour is the flashing rainbow colours in opal. Adularescence is the floating blue light that floats over a moonstone, a variety of feldspar Colour-change a distinct colour change in the gem s hue depending on its light source. Gemstones exhibiting this phenomena are alexandrite chrysoberyl, a fancy sapphire variety and a few very rare varieties of spinel and garnet. Also documented and exceedingly rare are colour change chrysoberyl catseyes. MOST OF THESE GEMS HAVE SIMILAR CARAT WEIGHTS BUT DIFFERING DIMENSIONS BECAUSE THEY HAVE VARIABLE SPECIFIC GRAVITIES. THE HIGHER THE S.G. ( DENSER ) THE SMALLER THE DIMENSIONS OF THE GEMS WILL BE WHEN COMPARING SIMILAR CARAT WEIGHTS AND PROPORTIONS. *NOT ACTUAL SIZE Be aware that even daylight is inconsistent. A gemstone looks different depending on variables of time of day, geographical location, weather and other lighting conditions. A gemstone you see on a clear day at 10 am in Bangkok will look different at the same time on a similar day in New York. Colour change Alexandrite Colour-change Garnets COLOUR CHANGE GEMSTONES SHOULD NOT BE CONFUSED WITH BI-COLOUR GEMS SUCH AS AMETRINE AND TOURMALINE. TRUE COLOUR CHANGE GEMS REACT TO DIFFERENT LIGHT SOURCES. BI-COLOUR GEMS HAVE TWO OR MORE SEPARATE HUES. Bi-colour Tourmaline MOONSTONE IS FASCINATING TO WATCH WHEN THE GEM IS MOVED. THE BLUE LIGHT FLOATS HYPNOTICALLY OVER THE STONE: ADULARESCENCE

CUTTING STYLES Quality Factors: the 4 C s? CABOCHON The 4C s of CUT, CARAT, COLOUR and CLARITY also impact a gemstone s value but in varying degrees and not in the same sense as it applies to diamonds. COLOUR is the most important of the 4C s for the coloured gem. BUFF TOP: FACETED PAVILION CABOCHON TOP BRIOLETTE SUGARLOAF SCISSORS CUT The value of these two aquamarines has been seriously impacted by the cut quality. While cut tends to not impact the value of gemstones as it does diamonds there are circumstances where poor cut is a serious detriment to value. Gemstones that tend to occur in light tones, such as citrine or aquamarine are often plagued by the window effect. Ideally, there should be no read through effect such as the pair of aquamarines pictured. (This is always more apparent with inclusion-free material). YOU SHOULD NOT BE ABLE TO READ THROUGH THE OVAL AQUAMARINE PICTURED RIGHT. Similar to the world of diamond cutting, the cut quality and the cutting style is selected to ensure the maximum beauty potential is reached of a given gemstone. However, many factors influence cutting decisions. The quality of the colour is the first priority, and in strongly saturated gems with dark tone, shallower proportions may be the best choice to create the most beautiful gem. The reverse is also true that a light tone gem with weak or moderate hue saturation would be best cut with deeper proportions. The original crystal shape and optical properties also influences the finished shape of a gemstone. The best example of this is tourmaline which is most often faceted in a rectangular cutting style because this retains the most carat weight and this crystal system is basically rectangular. The cutter must orient this doubly refractive gem for optimum overall hue. Tourmaline especially can appear over dark if cut in the wrong optic axis direction. FANTASY OR FREEFORM FACETING CHECKERBOARD (NO TABLE FACET) AND OF COURSE, THERE ARE MANY VARIATIONS OF THE TRADITIONAL FACETING STYLES. CARAT WEIGHT Gem materials vary greatly in density -- amber may float in salt water (density near that of water), while hematite is more than five times the density of water. This is why two different gemstones may have the same size but different weights and vice versa -- a one carat round brilliant diamond of typical proportions will be approximately 6.5 mm in diameter, while a round brilliant ruby of the same size (6.5 mm in diameter) and proportions will weigh approximately 1.55 carats. Generally, gemologists refer to specific gravity, or relative density -- the ratio of the density of a gemstone relative to that of water. There is a natural link between the carat weight of a gemstone species or variety that impacts the gem s overall rarity. For instance colourless topaz crystals may occur in massive sizes of thousands of carats and tsavorite garnet rarely occurs over a 2 carat weight. Consider the natural occurrences of the corundum species. Sapphires are not particularly unusual in 4-5 carat weights but rubies are quite rare in this range and their value per carat increases exponentially past the 4 carat mark. THIS 45 CT AQUAMARINE PENDANT, ALTHOUGH BEAUTIFUL IS VALUED PER CARAT NEARLY EQUAL TO AN AQUAMARINE OF 20 CTS. THE 45 CT GEM CAN REALLY ONLY BE SET IN A PENDANT OR BROOCH. THE 20 CT GEM IS MARKETABLE AS A RING STONE, WHICH IS MORE DESIRABLE. There is also a set point where the value of some gems are less valuable in high carat weights. Aquamarine is often priced less per carat when 20 carats or greater verses a lesser carat weight gem. This is because the larger aquamarine has less versatility and this affects it marketability. (Large aquamarines are not particularly rare ). Other gems affected by overweight-ness are amethyst, citrine, and blue topaz. It is not necessarily so that a very large gemstone s value will be high.

CLASSIC LILY PAD INCLUSION IN PERIDOT DENDRITIC FORMATIONS IN QUARTZ METALLIC INCLUSIONS IN SAPPHIRE CLARITY What is the best clarity for a gemstone? The best answer to this is : It depends. Clarity is often the most misunderstood feature of a coloured stone s value. Generally speaking, if the naturally occurring inclusions do not interfere with the gemstones durability or beauty they will not greatly impact the value of the gem. Eyeclean gems, meaning there are little or no eye visible inclusions, are usually the most preferred. Unlike diamond grading, clarity is not as strictly judged under the 10x magnification guideline for quality assessment. Some gemstone varieties always occur with natural inclusions and when these are less apparent, higher value will result when colour quality is also good. Some gemstone varieties (like aquamarine and topaz) occur nearly inclusion free as the norm so clarity judgment is a less important factor for rarity to affect the value conclusion. Quality Factors the 4 C s COLOUR...is everything for a coloured stone! While we now understand how hue, saturation and tone are used to describe colour in a gemstone, it is the optimum combination of these three factors that govern the gemstone s value. This optimum combination is different for each gemstone and relies on the whims of nature. As you view our showcases and reflect on what you have learned about gemstones, it will become obvious that the optimum combination for any gemstone is the Birks & Mayors sought after ideal. Value increases dramatically when certain gems are of the best colour possible and couple this with rarity as the single greatest denominator. It is possible for an eye clean red tourmaline to mimic the best eye clean ruby colour in a 4 carat weight. The ruby will always be greater value because of its rarity. FEATHER INCLUSION EXHIBITING LIGHT INTERFERENCE CROSSED ELBAITE CRYSTALS IN TOURMALINE And some gemstone varieties depend on the presence of inclusions to be valuable! Star sapphires are the best example of this since asterism is not possible in an inclusion free gem. Inclusions, in their own right are actually quite beautiful! Consider this inner space of a gem another feature of a gemstone s beauty and if you are comfortable describing and showing the inclusions under your store s microscope make sure you preview the gem first to be sure the higher magnification (at least 20X) does not make a mountain out of a molehill. Very often, inclusions if eye visible and if noticed after purchase, are mistaken for cracks or other damage so it is a good idea to be somewhat familiar with the natural appearance of inclusions. WHAT DOES A RACEHORSE HAVE IN COMMON WITH A FINE COLOURED GEMSTONE? A RACEHORSE THAT CAN RUN A MILE A FEW SECONDS FASTER IS WORTH TWICE AS MUCH. THAT LITTLE EXTRA PROVES TO BE THE GREATEST VALUE. THE SAME IS QUITE TRUE FOR COLOURED STONES. A LITTLE EXTRA COLOUR OR EDGE IN SATURATION IN A GEM FROM STRONG TO VIVID INCREASES VALUE SIGNIFICANTLY. SILICON DIOXIDE INCLUSIONS IN AMETHYST LIMONITE DISC INCLUSION IN TOPAZ PYRITE INCLUSION IN PALE AMETHYST COLOUR ZONING FROM CRYSTAL GROWTH INCLUDED CRYSTAL IN GARNET TWO PHASE : CAVITY AND GAS BUBBLE IN AMETHYST THESE TWO TOPAZ, ALTHOUGH ATTRACTIVE, DIFFER GREATLY IN THEIR VALUE. LEFT HAS LOWER SATURATION COMPARED TO THE RIGHT IMPERIAL TOPAZ WITH THE SLIGHT NUANCE OF RED AND STRONGER SATURATION. THE TOPAZ AT RIGHT IS NEARLY THREE TIMES GREATER VALUE THAN THE LEFT.