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