Gemstone Vocabulary and Anatomy

I decided to put together a glossary of sorts of gemstone terms, or terms that I use relatively often and might not be familiar to those who aren’t well versed in gemstone and jewelry terminology. Something I wish I had when I was first learning!

This is an endlessly growing and changing document, and will need continuous updates to keep it useful. Please let me know if any suggestions for terms, or comments you might have!

Adularescence – milky glow that moves as the stone moves, originates from within a gemstone and is caused by inclusions, occurs in the presence of stronger light conditions.

bezel set – a way of setting a stone with solid metal completely surrounding the stone, pushed down over the stone’s girdle

brilliance – amount of light reflected back out of a gemstone, a direct result of a stone’s refractive index

brilliant cut – a facet design radiating from the culet of the stone, on a perpendicular plane from the girdle of the stone

cleavage – tendency for a mineral to break along distinct planes dependant on how the mineral grows

colorless – a stone that is not known for being without color, having zero saturation. Examples: sapphires, spinels, garnet, tourmaline, topaz

crown – the facets from the girdle up to the table, the height from the girdle to the table

culet – the pointed tip of a stone formed by pavilion facets. Antique diamonds may have “small” “medium” or “large”. Modern cut diamonds typically do not have a culet, the pavilion facets meet at a point.

dispersion – the ability for a gem to divide the light into spectral colors

facets – a flat plane cut onto a gemstone

fat belly – when a pavilion is cut to preserve weight, instead of forming a cone, it is more bulbous and round on the bottom

fire – see dispersion

fluorescence – reaction of trace minerals causing the stone to glow a specific color when exposed to UV light, typically blue, yellow and red

girdle – the circumference around the stone where the crown and the pavilion facets meet, it can range from very thin to very thick, and can be faceted or rough.

keel – an edge formed by pavilion facets. typically found in elongated cut stones

kozibe effect – culet reflected around the stone

luster – light reflected from a gem’s surface

meet – the edge in which is made when two facets line up in faceting

monochrome – varying tones of one color, white-gray-black

MRB – modern round brilliant

OEC – Old European Cut

OMC – Old Mine/Miner’s Cut

pavilion – the bottom part of the stone, typically cone shaped

pleochromism – the characteristic of having different colors visible from different angles

RI – refractive index

Rose cut – stone cut into a dome type shape with a flat bottom/no pavilion, and the crown is a hexagon shape with triangular facets, meeting in a low angled point on top, typically cut in a round shape, but may also be cushion, pear, oval or marquise.

saturation – how pure and intense a color appears. Low saturated tends to be gray, highly saturated is vividly colored.

silk – the appearance of a stone looking slightly cloudy, which bounces the  typically caused by inclusions referred to as silk,

spread – the size of a stone when looking top down, measured by the diameter of the girdle. Typically used to compare one stone to another.

step cut – a facet design on a parallel plane from the girdle of the stone, typically angular in shape. Emerald, baguette, carre, asscher are common types.

tilt window – when a stone is viewed at an angle that is not straight down into the stone, and you can see through the pavilion

table – the flat top facet of the stone

window – when a stone is cut at the wrong angles for it’s type, the see through portion in the middle is called a window

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Window illustration

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Gem Blast: Small Diamonds

Using the term “small” here is kind of facetious, being that the rounds aren’t exactly tiny, hovering just under the .30ct mark each, and are larger than some people’s engagement rings. The round stones are about 4mm each, antique cut, mostly Old European Cut diamonds, but with some early modern round brilliants as well. All seven of them end up totaling about 1.9ctw.

7d

7e

 

Some people refer to these small square diamonds as being “square step cut” or “square baguettes” but I call them carre cut. They distinctly do not have cut corners or windmill type facets cut into the pavilion, and are actually quite simple in their cutting style. They are thought to be predecessor to the princess cut.

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I love sprinkling diamonds onto a surface and photographing them as they lay. I am not a diamond girl, even though I was born in April, and until recently stuck almost exclusively to colored gems. Recently I’ve come to realize that diamonds are nice too, just not nearly as brightly colored.

7a

 

I don’t actually have any kind of grading on these round cuts, and they are not perfectly matched, because if I wanted perfectly matched antique stones, I might die before finding them. But I think as far as color, clarity and size, they are well matched.

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The carre diamonds are around 2mm, and some are chipped, as you can kind of make out in the picture. They originally came from a yellow gold 1980s band, and were channel set, along with a lone princess. I imagine that a jeweler decided to replace a carre with a princess since carres are not exactly plentiful unless you know where to look. They total about .30ctw since they are so small. They have very flat crowns with large tables, and therefore face up large for their size.

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I have a love affair with step cuts, and I love the big flashy facets from OECs, so these two little parcels are some of my current favorite stones.

 

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Both sets of these stones will probably be going into bands at some point, but specific plans have not been made yet, just ideas floating around in my head for now!