Jewelry Part V - Jewelry & Gemology Primer

BRG Primers 101 | PUBLISHED 01.08.21 | Jennifer Ventresca
Blingology - Jewelry & Gemology Primer | BRG


(Jewelry & Gemology Primer)


Gems come in all different shapes, sizes and colors. Some have been mined centuries ago and are part of the antique jewelry and estate jewelry markets, while others are "younger" (mined more recently) and qualify as vintage and contemporary gems. Whatever the shape, size, color, or age, as part of our ongoing jewelry blog series, we venture to give you a solid overview of gemology and the use of gemstones in jewelry...

Some of the ubiquitous terms used when grading and valuating gemstones hail from the "4 Cs" of gemology. For the sake of this blog, we've added "contrast" in there too -- so it's more like 4 Cs plus one.

4 Cs: an universal grading system developed by the Gemological Institute of America (GIA) to evaluate the quality of a diamond. They include Carat, Color, Clarity and Cut.

BRG BlogCarat: unit of measurement for weight of precious and semi-precious gemstones and pearls, mass equal to 200 milligrams or 0.00643 troy ounces.

Color: used to grade precious stones, particularly diamonds. The GIA (Gemological Institute of America) color scale ranges from D to Z, D being considered colorless and higher in value

Clarity: used to describe the presence or absence of a gemstone's external or internal flaws.

Cut: (not to be confused with shape!) cut is a factor determining a diamond’s brilliance; qualifies brilliance, fire, and scintillation by analyzing proportions, symmetry, and polish.

Brilliance: refers to brightness and contrast of a precious gem (particularly diamonds);

Brightness: refers to the amount of light returned from a diamond’s surroundings and back to the observer.

Contrast: intensity of white light from crown of stone

Very often, when people think of gems or gemstones, they immediately think of birthstones. While there are a vast variety of gems (precious and semi-precious) that fall under the realm of gemstones, we would be remiss if we didn't at least provide a quick summary of the traditional birthstones.

Birthstone: a precious or semi-precious gemstone associated with the month of birth.

January – Garnet

February – Amethyst

March – Aquamarine

April – Diamond

May – Emerald

June – Pearl

July – Ruby

August – Peridot

September – Sapphire

October – Opal

November – Citrine

December – Topaz.

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As for everything else in the extensive world of gemology, here is a brief primer on some of the most common terms with some examples from BRG's own jewelry lab or past auction offerings.

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Accent Gems:

Gemstones which complement a center gemstone and side gemstones. These are not the main focus, and are typically comprised of melee gemstones. See also melee gems.

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a polished convex cut unfaceted gemstone gemstone whose resulting form is usually rounded with a flat reverse (underbelly).

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a relief-cut design typically into a hard gemstone or shell.

Center Gem: the main gemstone in the design; typically the focal point of the jewelry piece.

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Claw / Prong:

a mounting wire used to secure a stone in a setting; setting method in which a stone is secured in place by metal claws/tines/prongs.

Scalloped: setting method in which prongs of a piece of jewelry are created from the shank.

Tension: a compression setting which holds a gem in place with tension, not prongs.

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multiple gemstones grouped together in a setting.

Crown: the faceted area of a stone located above

Cubic Zirconia: also known as CZ. It's a man-made simulated diamond gemstone.

Culet: the base point of a gemstone or diamond.

Depth: the length of a stone from its table to culet.

Diameter: the overall width of a gemstone.

Facet: the flat, polished surface of a gemstone or diamond usually with three or four sides.

Gallery: negative space located on a head/setting.

Head: Also known as the setting; it's the part of a piece of jewelry that secures the gem.

Gemstone: an organic or mineral crystal which, when cut, shaped, and/or polished is used to make jewelry or other adornments. Also called gem, jewel, precious stone, or semi-precious stone).

Genuine Stone: a gemstone which is produced naturally, without interference from mankind.

Girdle: the widest part of a faceted gemstone; separates the crown (upper part of stone) from the pavilion (base of stone).

Inlay: insertion of pieces of gems into slots cut into the surface of a piece of jewelry for embellishment.

Melee Gems: a classification used in the sorting of diamonds and gemstones weighing less than .17 carats or 17 points each.

Moissanite: a rare material discovered by Henri Moissan, which was later laboratory synthesized and used as a high-quality substitute for diamonds.

Mounting: jewelry item with stone settings minus the stone(s).

Setting: refers to the base holding a gemstone in place; styles of settings enhance the stone's beauty as well as the overall brilliance of a piece of jewelry, also known as head.

Bar: the gemstone is secured between two parallel bars, while the sides fo the gem remain open

Basket: a type of prong setting with open sides (like a basket weave) which allows the lower part of a gemstone to be visible.

Belcher: a ring mounting where the stone's claws or prongs are cut into the shank of the ring so that the gemstone does not extend above the circumference of the shank.

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method in which a band of metal encircles all or part of the stone that secures a gemstone in place.

Buttercup: style that usually consists of six prongs connected to a scalloped base resembling a buttercup flower.

Cathedral: a traditional style of mounting that uses arches of metal to hold the stone high above the shank, adding height and the appearance of a larger stone.

Channel: a mounting in which a series of stones are closely set into grooves between two parallel walls; forming a row that may run along the entire band of a ring.

Flush: a mounting technique in which a stone is embedded into a hole which was drilled into the metal and metal is hammered around the stone to secures it.

Illusion: a prong setting designed to make a stone appear larger than it actually is

Invisible: method in which there are no visible prongs or supports; stones are grooved so that a thin wire framework secures them to the jewelry piece.

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a jewelry style where the entire surface of the piece is covered or "paved" with closely set gems.

Pavilion: refers to the bottom part or base of a gemstone.

Precious Gem: class of gemstones consisting of diamonds, sapphires, emeralds, and rubies.

Remount: removing gem(s) from one jewelry piece and setting it (them) into a new item.

Semi-Precious Gem: class of gemstones that are not precious (diamond, sapphire, emerald, or ruby); these include stones such as peridot, aquamarine, topaz, amethyst, garnet, etc.

Side Stones: complementary gemstones that emphasize the center gem.

Simulant: imitation gem which is sold as a "look-alike" for another gemstone; it may be natural or artificial/man-made.

Table: the flat, top part of a cut gemstone or diamond.

Treated Gems: Refers to the practice of enhancing or altering the natural state of a gemstone chemically or conditionally. Types of treatment might include: heating, oiling, Irradiation, dyeing, or bleaching.

Untreated Gems: gemstones which have not been enhanced or altered in any way other than polishing and/or cutting. They exist in the same form as when they were first extracted from the earth and only get polished.

Next time ...

Jewelry Part VI: Jewelry Metals

If you would like to learn more about your own jewelry (valuation, whether it's real or fake, etc.), send us an email. Someone from our expert jewelry team will be happy to help you.

Keywords: gemstones, gemology, jewelry, carat, color, clarity, cut, brilliance, brightness, contrast, birthstone, settings, precious, semi-precious, gemstone, gem

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