A Glossary for the Novice Gem Buyer

By: Edward Bristol

Appraisal: 3rd party financial judgment about a stone or jewelry. To be distinguished from a "certificate" and a "grading report".

Bead: Smooth round polished gem.

Belly: Wide shape in the lower part of the gem. Generally pushing up the total weight. Must not be ugly but is expensive when compared to a ideal cut stone without belly but an equally sized "face".

Bi- or Multi-color: Gem exhibiting more than one color in the same light and position. Nearly every gem shows different colors in different lights and angles. This is not called multicolored.

Black-out: Parts of a gemstone which do not throw back light and thus seem dark. This is also called "extinction".

Bleeding: This is a term for an unpleasant loss of color and saturation in different light settings.

Cabochon: Smooth polished gem, usually single sided when to exhibit stars or cats eyes. Also used on rough gems which are too included to have luster (when faceted) but have a good enough color to be attractive.

Carat: Weight dimension for gemstones. Equals 0.2 gram. For the visual size of a stone of a stone you have also to look at the dimensions and shape. A round and deep two carat stone might actually look smaller than a princess cut one carat stone. Important for jewelry is the "face" of a stone. Ideally you want a stone having a big face but no "window".

Certificate: Gemological report (not "grading report" or "appraisal") about a gemstone. Must be issued by an independent 3rd party company. They start with simple variety identification for $25 and go up to comprehensive scientific studies for several thousand dollars.

Chip: Surface flaw, usually caused by sudden temperature changes during transport or pressure during setting. Heated stones are more likely to chip.

Clean: A gemstone without or with very few inclusions. A gemstone is clean if you need a lens to see the inclusions.

Color Change/Shift: A color change gemstone will change its color when moved from day- to artificial light. If the two colors are very close to each other (e.g. violet and blue or red and purple) it is more accurate to speak of a color shift. Most gems show some sort of color change in different lights but only an obvious strong change would justify an extra charge. It should be mentioned in the "certificate".

Cooked: Heated gemstone. Heavily cooked gems adorn 99% of all ready to buy jewelry.

Crystal: A good crystal is one of the most mysterious qualities of a gemstone. Connoisseurs do use the term freely, yet it is hard to make them define it. Probably it is best understood by its antonyms: A bad crystal is dull, cloudy, indifferent, non-thrilling, undefined, muddy, fuzzy, boring etc.

Cut: Process and result of faceting and polishing a gemstone.

Dead: Rough that will not have luster after the cut, or a very badly faceted gemstone with no luster, mostly due to inclusions or a very bad "crystal".

Energy: Expression used to describe a gems character on an emotional level. One may clearly perceive a gemstone as tranquil, intense or lively. Not scientific but often helpful.

Extinct: Gem which does not throw back light and thus seems dark. Also called "Black-out".

Face: The upper dimensions of a stone which is visible after being set in jewelry. Sometimes also referred to as table. The face is the most important feature to look at when judging a gemstone's size for jewelry.

Faceting: Cutting and polishing a rough gemstone.

Fish-eye: Term for a gemstone with a big "window". For diamonds the term is also used when a pavilion is cut too shallow, allowing the girdle reflection to show through the crown.

Fluorescence: Though scientifically not correct, the term is use to describe a gem's (especially a rubies) capabilities to glow on its own. In fact, the stone re-emits ultraviolet light.

Gemologist: Anybody knowing enough about gems. No protected profession.

Grading: Process of evaluation by a "gemologist", in particular the owner of the stone and thus including subjective non-qualitative characterization and overall rankings. Hence grading is to be differentiated from "certification" in which a 3rd party testifies only the stones quantifiable features or a financial "appraisal".

Grown: Grown is a term often used by fraudulent sellers to skip around the fact that their gem is synthetic and, therefore, worthless.

Hunting: Search for an individual gemstone based on a buyer specification of size, color, cut etc.

Hypnotic: Term used for the very best colors. Such a hue will imprint itself into your memory and will never be forgotten. It is quite a compliment for any gem.

Imitations: Anything pretending to be a gem without being one.

In the color: Sales term to describe the quality of a color as being best in that hue. Subjective judgment.

Inclusion: Anything that hinders light falling through and out of the stone. Some inclusions are desired (horsetails, needles, silk) others not (cracks). Some can be very aesthetic (water lily) others are not (dirt). If you can't see an inclusion with a 10fold lens, it does not exist for grading purposes. If a stone has no inclusions under the microscope (rare) it can sometimes not be distinguished from a synthetic. Inclusions are also essential to determine treatments.

Inspection period: Agreed upon period in which a buyer can decide to return the stone or a parcel.

Lapidary: Person or company faceting gemstones.

Lens or loupe: Small, handheld and mostly foldable, glass with 10 (standard for grading) or 20fold (sophisticated) magnifying power. Inseparable from any professional gem trader and collector. Should be neutral in frame color and a triplet. Cost: between $2 and $100, with $20 doing fine.

Lot: Big "parcel" of gemstones.

Mine-run: Most professional mines are organized in time-phases based on weather seasons or work cycles. For example, a mine team may dig out gem bearing gravel for one week and then wash the gravel in the next week and thus concluding one mine-run. Many mines actually have annual mine-runs, e.g. digging in the dry season or in summer and then washing in the rainy season.

: Gemstone formed in geological processes without the help of humans or simply: non-synthetic.

Off-center: Cut in which the back does not close in the middle of the gemstone but off the center. This mostly happens when the lapidary, in order to keep weight and luster, follows the natural shape of the rough stone. The alternative to being off-center is usually a "window" and much less weight. The luster of such stones often runs unequal or leans towards one side. Nevertheless, being slightly off-center is not considered a major flaw but only a lesser evil as compared to a "fish eye" in half the size.

Off-color: Hues outside the classics like cornflower blue, maize yellow or rose red. Off-color does not mean ugly or unattractive but simple currently not in fashion in a specific variety. Off-colors can be good investments and are often just as beautiful as classical hues. A color that is most desired in one variety can be off-color in another variety, like yellow brown chrysoberyl cats eye (in) compared to yellow brown sapphire (out).

Offer: Making an offer is to name and commit to a price you are willing to pay for a gemstone. Taking back an offer without very good reason is deemed rather impolite in the trade and might result in being shunned next time.

Opaque: No light falls directly through a stone. Some varieties are opaque by definition (opal) while others may be just very included.

Origin: The place where a gem is mined. An origin can be different from the "country of manufacturing" which, legally and for tax purposes, is defined as the place where a stone is "cut". Premium origins like Ceylon or Burma command higher prices.

Pad: Short form for padparadscha, a rare orange pink sapphire.

Pale: Other word for light tone. A pale stone has little "saturation".

Parcel: More than one gemstone sold for a package price. As a rule, if you negotiate a parcel price you cannot later cherry-pick from the parcel but you either have to take the complete parcel or reject it.

Point: 0.01 carat. Measure used for smallest stones (to make it sound bigger). For example 10 points is 0.10 carat, which is really small but doesn't sound so bad. Mostly used for diamonds.

Recovery: Percentage of a gem that remains after cutting and polishing the rough. A realistic recovery rate is 20%. Thus one needs one gram of "rough" to make a carat of final gem. The term is also used to describe the loss in re-cuts, e.g. from an emerald cut into a scissor.

Rough: Uncut unpolished gemstone including crystals. Often illegal to export from 3rd world countries without special permission.

Saturation: A 100% red saturation theoretical means there is nothing but red in a gem. In reality you will always have secondary hues and grey tones. However, a red gem with 80% saturation is very red and you will probably not recognize anything but red.

Semi-precious: Criticized term for less valuable gems. Most people in the trade agree that it has no meaning but continue to use it to differentiate between high-end collector stones and cheaper gem material. Some previously semi-precious stones like red spinel or chrysoberyl have sure entered the precious realm. However, just because something is called sapphire or ruby does not mean that it is precious. In fact 95% of all that is sold as ruby or sapphire does not even qualify as semi-precious while some amethyst or garnet may be relative cheap but can be high-end collector items and are surely precious.

Setting: The setting is what makes a gemstone wearable in jewelry.

Shape: General outer form, like square or oval, of a gemstone.

Sleepiness: Special quality attributed to high-end rubies and Kashmir blue sapphires due to very fine invisible needles shattering light rays.

Sustainability: Usually describing non-destructive and maintainable use of natural resources, as opposed to overexploitation. In the gem trade, with basically non-renewable resources, the term is used to express concern for environmental and social welfare in the mining countries. Non-sustainable mining would describe the exploitation of gem resources without improving the local life conditions and leaving the place polluted in the process.

Synthetic Gem: Man-made reproduction of a natural gem.

Tint: A fleeting idea of color in a white gemstone.

Tone: Degree of lightness or darkness. A lightest tone will be nearly colorless (white/grey) with just a "tint" of color, while a very dark tone will be nearly black. Ideal tones vary from variety to variety, e.g. pads are said to be best in a light tone while blue sapphire can be rather dark.

Translucent: Half-way between "opaque" and transparent. Often found in cabochons.

Treatment: Any alteration of a natural gem to improve its appearance. The most common treatments are heating, radiation, fracture fillings and lately Beryllium treatment. The border between treating and cheating are flux. It is considered permissible to sell heated sapphires as long as the stone is disclosed as being treated. Especially stones in jewelry are however rarely labeled correctly but are nearly always heavily "cooked". Though not illegal, Beryllium treatment, filling or radiation could be called cheating because a gem trader can sell something practically worthless or potentially dangerous as a precious gemstone.


: Non-synthetic gem that has not undergone any man-made changes other than faceting and polishing. This is the only type of gemstone that will maintain its value after you bought it.

White: Colorless.

Window: See-through center of a shallow stone. Windows are especially disturbing in light colored stone because they create a "fish-eye" effect and do not reflect light back. The darker or more intense a color, the less a window is to be worried about. You may snatch a color bargain if you don't bother about a window.

Zoned: A gemstone is said to be zoned if there are layers or patches of color or areas of no color. Mostly unwanted, unless in multicolor gemstones where the shape, regularity and clearness of color zones is highly priced.


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