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: Emeralds

Emeralds are considered one of the four “precious gemstones” along with ruby, diamond and sapphire (blue, specifically, since, you know, red and pinkish sapphire is typically considered ruby. But whatever.) So that means that they are highly prized, highly synthesized and highly treated.

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But it’s the birthstone for May so I’ll do a post on it, especially because I am lucky enough to have had two fantastic specimens in my hot little hands for the moment and of course have photographed the heck out of both.

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I have a special place in my heart for green. It was my favorite color from roughly age fourteen until about seventeen. And no other gem does green quite the way emerald does. Here is an gorgeous Afghan tourmaline to illustrate this point:

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And a green beryl/Aquamarine:

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One of the things that makes emerald so special is the glow that seems to light it up from the inside, almost like a green light on a stop light. Fittingly part of what gives it this look is “jardin” the name for the inclusions within emerald, French for “garden”. The only time emerald really seems to “sparkle” is when it’s incredibly clean and without jardin, but this variety of emerald has an entirely different look and feel to it, more like a bright green aquamarine than the soft, but intense glow of a stone with jardin.

Close up with the smaller of the two. Both are Colombian in origin.

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This particular emerald doesn’t have a ton of inclusions, making it pretty rare for an emerald. Just enough jardin to give it that glow factor, which is so highly sought after in these green beauties.

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The larger of these two beauties is for sale, and I keep restraining myself from thinking about setting ideas for it.

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But I still have the little one to play with. I was thinking something Art Deco would be awesome…and emeralds always look amazing with diamonds!

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Maybe I need to hit up the sketchbook…

Feature: Lang Antique & Estate Jewelry, Bonus!

So I took a ton of photos while I was at Lang Antique & Estate Jewelry , but some didn’t come out as well as I hoped. Here are a few pieces that I was able to take more than a couple seconds to get a quick snapshot.

I don’t typically love trillions for myself, but I thought this ring was really interesting and wonderful because of the flow of the design and the way it all melds together into one giant piece of stepcut and brilliant cut awesomeness. I love the graduation of the step cuts and how they mimic the lines of the trillion, giving the whole piece an Art Deco vibe.

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I don’t think this one really needs any commentary.

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I loved this little band, it really had some great details to it.

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I absolutely fell in love with this necklace. The larger of the two stones was a low colored diamond with the smallest table I have ever seen on an antique stone, and as a result was super fiery and all around fabulous. I thought it was the perfect size to be able to wear it on a daily basis and not have it be too overwhelming of a piece, easy to dress up and dress down. I believe the total weight on it between the two diamonds is around 1.1cts.

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And for the Grand Finale!

This is in the store window. It is almost 7cts of magnificent French Cut brilliance and it is one of the most fabulous items I have ever seen in real life (having been NYC and seen the Tiffany Diamond in all it’s glory, I think that’s probably a pretty big compliment!). This stone is interesting because a hole was drilled directly into the stone and a ring through it, to hang it on a chain. You don’t see this done a lot with diamonds, especially not of this size and cut. I am guessing it was done because of an inclusion, but obviously I was not the person to do it to the stone, so I can’t really say why it was done. I would like to see it on a different chain though, rather than this round diamond chain. I feel like such an amazing and expensive diamond should have a custom piece built around it.

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Next time, I’m going to have to set aside another hour, and I plan to try on everything that I saw in the front window. Ok, maybe I might need two hours…

Ok, that’s really it for my visit to Lang! Hope you enjoyed the pics, next time I’ll get video of the big french cut in action!

Gem Blast: Considering Gemstone Recuts

I typically like to do Gem Blast posts as mostly pictures with little commentary, as it gives me a little break from writing, and I get to post pictures, which I love taking, but this one is a little bit different because it deals with a specific issue: Gemstone Recuts

This stone started out coming to me from ebay, and is a hot pink spinel from the Mahenge area of the Morogoro region of Tanzania. It was 1.8cts, and 7x6mm. It wasn’t until owning this stone for well over a year that I realized that it had a horrible crack in the pavilion, along the keel. I enlisted the help of  Jerry Newman of Gemart Services to see if it could be cut out and let me tell you, that man is a miracle worker.

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Amazing color! But if you look carefully at the above left image, you can see something funky going on on the keel from the face down view. But when you flip it over and look at the keel through a macro lens, it makes sense.

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So I sent my stone to Jerry. He had said that he thought he could get rid of that nastiness without it affecting the face up size. Once he was done, and he is very very fast – I got the “It’s done!” email less than a week after he got it – he said that he thought he could recut it again and make it more brilliant, but he wanted to know my opinion. After the recut:

 

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Obviously I liked the stone just as it is, and didn’t want to lose more material or risk the loss of more saturation. It is difficult to tell because the environmental situations are different from the “before” pictures, but the stone lost a little bit of saturation. However, Jerry managed to only recut the pavilion with no loss to the face up size. It went from 1.8cts to 1.55cts, and actually became more stable since the liability of the crack on the bottom was eliminated. The clarity was improved as well since the fuzziness that the crack created went away.

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Because of the overwhelming success of the above pink spinel, I have started considering recutting a few other stones of mine…

Silvery spinel, 5×7, considering a recut on it to improve performance. It currently has a small window, and a bowtie. Sometimes it even shows a bit of half and half shadowing. I think it’d be gorgeous if it had some improved cutting. It has a bulgy pavilion, so recutting it should be relatively simple and improve it significantly. I actually think the stone is nice to begin with, with a really cool light gray, but I think the risk is small enough and the payoff good enough that I think it should probably be done.

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Possible Emerald Tourmaline recut. This is a different case because this stone started out as a precision cut stone from Master Cut Gems. It has a gorgeous color, but it was very badly chipped (mangled?) when it was set in a setting. Unfortunately I didn’t realize this until long after purchasing the original ring. Luckily I had a stone that would fit into the setting, so it wasn’t a total loss, but the stone is pretty much unable to be reset because it’s so badly damaged. Here is a picture of the stone from Dana at Master Cut Gems before it was set:

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Beautiful color, eh? It’s a great teal, not too dark. And here is the stone after being unset, under my macro lens, which makes everything look dark and shadowy, since it is black:

 

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You can see in this image how smoothed out the chipping is, with no sharp edges, showing that it was done quite some time ago, and is not new damage:

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I have a macro picture of the stone in the setting, and you can just barely make out the mess under the one set of double prongs. This is the mess on the opposite end:

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Another view, giving an idea of the slight bicolor (green on one end, blue-green on the other) action going on with this stone, as well as showing the wear on the facet junction on the meet between the crown and the table facets.

 

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So, I’m kind of playing with the idea of seeing if it would be possible to cut all of the bad stuff away, and leave something that could be used. I have talked a little bit before about my love of all things step cut, so it really pains me to chop this up, but I think there might be potential to cut another step cut out of it, perhaps a shorter emerald, a carre or an asscher. Unfortunately, this stone is a smaller 1.07ct (the chip is probably big enough to decrease that!) so it’d probably end up being about 5×5 and maybe .60ct, so I don’t know that it’d make a lot of sense to do it, but I might do it anyway because it’s such a great color.

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Gemstone recutting, or cutting of rough is not a job to be taken lightly. It takes an immense amount of talent, intestinal fortitude, luck and knowledge to produce these small sparkly items. I have nothing but the utmost respect for lapidaries because it is not an easy job, and clients can be hypercritical of the results. I greatly admire those that do it, especially recutting damaged stones and cutting from customer’s rough because of all of the risk involved. Every time I have gone into a jewelry project with something I’m unsure about, I have a pit in my stomach until it is completed, and when the risk is the total ruining of a gemstone, the risk is really quite high, and not something to be attempted on a whim.