Faceting

This stone is a blast from the past. I cut this when I was first starting to get into cutting and wanted to see how long a rectangle I could cut. This turned out nice but was, as I recall, a super hard cut to complete. The length of the rectangle caused issues during transfer and I had to make minute adjustments while cutting the crown.

I had an offcut from my Smith Bar, so I did a simple brilliant cut to make sure that I could actually get a proper polish on the aquamarine crystal. Turns out it was definitely something with my technique in the last stone.

I did this to show the difference RI and other stone attributes affect how a cut looks. This cut was designed to look like the cockpit of the millennium falcon as it enters lightspeed, which I designed specifically for my niece who is a HUGE star wars fan.

Here it is in quartz:

And in London Blue Topaz:

Just goes to show that a single design may not work well in all materials.

So I've never cut one of these before, and frankly I'm not sure how it would turn out.

Let me know your guess!

(I should have a new stone finished this weekend which I'll share Monday.)

Here is another video by Justin on just what is precision cutting.

Had a crack at the Smith Bar, by Jeff Graham. Usually I'm fine polishing beryls but this guy just wouldn't behave, possibly due to the extreme angles I needed to do.

I've been faceting since October last year and finally got the guts to do a frosted design. The colour is a bit washed out - it's greener in real life, but mobile phone colour correction always kills it. One day I'll figure out how to actually take nice pictures of gems.

Design is Frost Star Hex by Andrew Brown

So I finally got my hand well enough to get back to cutting and finished the first of two calibrated 4mm stones for earrings for my daughter. This is the first one which comes in at 4.04mm.

This is the second attempt at cutting this stone, as the first one ended in failure when a fracture appeared in the center of the original rough.

The design for this cut was done by my son who wanted to try his hand at designing a cut. His design turned out great, and wasn't too hard to cut!

So I injured my hand and can't cut for a few days, so I thought I'd share some images of more esoteric gemstones to challenge those following to identify the rough. (Yes I know what it is...)

So what's your guess?

This was another commission I did for a co-worker who wanted this as an anniversary present for his wife. I picked up this piece at the Tucson Gem and Mineral show. It was not super saturated, and the shape was already close to a pear shape. I was really happy to get a 51% yield from the rough on this, and it turned out really nice.

This was a commission of a piece of rough I was asked to purchase at the Tucson Gem and Mineral Show a few years back. I cut it using a design by Arya Akhavan called Aperture Science.

There are a plethora of designs that can be found online and cut. The two sites I look through for ideas:

Gemology Project

facetdiagrams.org

Take a look through those databases, and I'm sure you'll see some really interesting ideas/designs.

A few years ago, just prior to COVID, I made the trek to the largest gem and mineral show in the world and one of the most dangerous places for my bank account.

Some of the display minerals, and yes they were for sale, are of museum quality.

Yes I know what you're thinking about that last one.... 😜

Some of these were made into chair, bench and table:

There were multiple sites across the city with vendors, all as large as this.

Vendors sold beads, geodes and almost anything related to minerals.

Of course what I came for was rough to facet, and there was tons of it. At some sites there were bins full of moonstone, amethyst and other facet grade stone. The best stuff was behind counters like this one.

Honestly I spent way too much, and still haven't cut all of the rough I bought. Since COVID I've heard it isn't quite as big, but is still worth the visit.

Let's see how much a variety of rough I have...

This cabachon was done a few months back for free for someone who had collected some stone and was curious if anything could be made from it. I normally don’t do cabs as I lack the optimal equipment but this person couldn’t find someone to help them out.

Here is the rough, not much to look at is it?

The dops I use for this kind of work are just wooden dowels. Here is the stone after I’d spent time shaping and grinding it down to find the color. The difference between faceting and forming a cab, is the cab is all done by hand without the use of a cutting head.

I did a final polish, then cut off the bottom to create a flat bottom surface.

I had a super color saturated piece of pyrope that was already bit thin and long, so I decided to see if I could cut it in shallow cut to compensate for the saturation. I had some success with this cut, but in the end it takes a LOT of light to get some good light return. This picture was taken outdoors in full sun, and you can see that there is very little light coming back through the stone, even though it was cut correctly for the refractive index and critical angle.

This was one of the first sapphire's I cut. It isn't the clearest stone, as it has a hint of cloudiness inside it. I do like the color, but wish I'd cut it a bit differently to bring out more light return.

So, in my last post someone asked me if I still had the stone I first cut. This is it, a plain piece of quartz. It's pretty large measuring in at around 18.5mm or just under 3/4 of an inch in diameter. The standard brilliant cut is not a hard cut, and is a great cut to start out with. If you make mistakes it still turns out nice.

One of the biggest mistakes I made on this stone was not properly aligning the stone on transfer, and ended up with the crown being lopsided from the pavilion. You can see in the above picture how I cut out the girdle on one side of the stone. I could be self critical about this stone and point out half a dozen things I did wrong, but why bother? That was many many many moons ago, and I don't make those mistakes nearly as often. 😜

Citrine is just one of quartz's color variants. Citrine and Amethyst are the most widely sought after colors, but it can also be found in a smokey color.

It's been fun digging through some of my early work and sharing. I'll keep posting in hopes of getting others to join in. 🙃

I cut this stone a few weeks ago for my daughter who wanted a triangular stone that could be set into a ring. I'd never had the opportunity to cut a trillion before, so this was fun.

Justin K Prim is a master cutter who has a youtube channel that has an incredible set of videos that talk about the art of gemstone cutting.

These two peridots I cut a while back with the aim of created a calibrated sized pair. Unfortunately the smaller of the two was cut second and I had to cut it down due to a flaw in the stone's girdle. Peridot is one of my favorite stones to cut due to how easy they are to cut and how they come out.

I've mentioned critical angle and refractive index in previous posts, but never really described what they are and how they affect light return and stone design. I'm going to discuss this at a very general level in this post.

Refractive index (RI): This is the speed of light divided by the speed of light as it travels through the material. The higher the RI the greater the angle that light bends at the interface between the air and material.

Critical Angle (CA): The angle which light is internally reflected rather than refracted.

Lets take a look at a semi-standard cut:

This design was done for Sapphires with a RI of 1.76, and a critical angle of 34.6 degrees. I'm only going to focus on how the light returns from a ray that is directly fired through the table. For this, we want to look at the last tier of the pavilion P5 which is cut at an angle of 38 degrees.

In the diagram above there is a light ray that shoots through the table and hits a facet on P5. The 38 degree angle is the angle shown and is greater than the critical angle, therefore the ray is reflected back into the stone.

The ray will reflect back at an angle of 52 degrees from the facet surface which is 90 - 38 = 52. It will pass across the pavilion and intersect at an angle of 24 degrees. This is because it forms a triangle and the sum of angles in a triangle must equal 180 degrees. As shown the interior angle of the cutlet (tip of the pavilion) is 104 degrees. Now testing the new intersection 90 - 24 = 66 degrees which is greater than the critical angle, and this ray will reflect back.

Obviously not all light rays will reflect back, many will just refract through the stone, and that's ok as that helps deepen the color.

For this cut the above graph shows how much light return happens based on how the stone is tilted left to right. The center of the graph would be looking straight down.

I am by no means an expert and have glossed over some of the details, but I hope this provides some insight for those of you interested in this interesting craft.

You can read a more detailed breakdown of the above at the US Faceters Guild Website

Beryl is interesting in that the most sought after color is classified under the name Aquamarine. I've seen and cut three colors total of beryl: golden, red and aquamarine.

Of the three I love the color of the golden beryl the most. This stone is also the first golden I cut, and is one I like to keep around for myself.

So this is a good example of great light return from a very saturated pyrope garnet. This stone I cut shortly after I first started cutting, and on machines that were not very precise. You can see how the cut isn’t very symmetrical near the table on the left side.

This stone like many others I keep around and don’t give or sell. They are good reminders to me that even if you make a mistake, and something isn’t perfect, it doesn’t mean you haven’t succeeded.

So a few years ago I got into trying to cut odd shapes. These shapes almost never make it into jewelry, but produce some interesting results. This one worked well for the small peridot I used it on. I got lucky in that the stone was already close to the final size, and ended up with a yield of 63% of the original.

My camera work has gotten a lot better since then. 😉