Faceting

Opal is one of the softer stones that is faceted. Many really only know fire opal that is formed into cabochons, that are white(or black) with a variety of colors reflected out. This type of opal is facetable and takes on the look of a flame with the light return.

I’ve come to not like cutting pear shapes, as they are very time consuming and hard to get the symmetry perfect. This stone has a very small fracture right at the tip that cannot be seen or noticed due to the light return. Even with that, I’m very happy with how this stone turned out.

I have this commission to cut a pair of 4mm pyrope garnets. Pyrope garnets are almost ruby red in color and can come very color saturated, meaning very very dark. These kinds of stones have to be cut a particular way or they will end up being too dark and not provide enough light return.

I found two stones in my inventory that met the needs of the commission, and both seemed like they would work well with little to no issues inside the stone that I could see with my loupe and a light source. So I started to rough the first stone out.

Well this isn't totally unexpected, as it being a super color saturated stone, I might have missed an inclusion. So the solution to this is to try and keep cutting through it to get past it.

Ok, now that doesn't bode well. Nothing to do but see how bad this is and keep cutting.

Ok, this stone is a total loss at the target size. The fracture runs through almost the center of the stone.

You can see clearly the section that is separated by the fracture when the stone is lit up. That section has to come off and doing so will make the stone too small for the commission. I'll have to go find another stone of similar color and size.

Sometimes lady luck is taking a vacation.

This cut is called a pear (or teardrop) and was a commission for a co-worker. I was still learning the techniques for taking photos/videos of stones so this isn’t the best quality shot. However, when this stone was in the outdoors with sunlight, it absolutely showed off a ton of red fire.

This was one of the first emeralds I ever cut, and given the quality of the stone (not super fine), I'm pretty happy about how it turned out.

Yes.. I'm going to keep posting in hopes of someone else adding their own posts to the faceting community. 😜

This stone I cut for my niece as a birthday present, and set it in a sterling silver pendant.

Thought I’d try and post some of my past work to keep the community active while I work on my current commission.

So I finished the problematic stone. I have to say this isn’t my best showing, but at least it’s done. 😁

I believe the stone came out slightly windowed, and does return the light as intended when looking through the table.

If you look closely at the girdle, it is wider on the right than it is on the left, as my vertical alignment was off after resetting the stone back on the dop after it popped off.

I’ll post something when I’ve finished the pair of garnets that are up next.

I started this problem stone this morning by cutting the facet that I was cutting when it popped off. It’s the left side, and you can see where the new cut started and how it is not level. This means the stone isn’t aligned either on the index, or vertically.

Nothing I can do about the vertical alignment, but I can realign the index using the cheater. The cheater is a dial on the cutting head that can make minute adjustments to the index. To realign I’m going to recut the entire crown as I have enough girdle left over to do so.

You can just see where the new cut on the center is coming down and is horizontally aligned with the girdle. I’ll finish this cut, then cut the facets I was cutting before.

You can’t really see it here, but as I feared the stone is not vertically aligned, and the girdle is thinner on the left than it is on the right.

I’ll finish and post the result in the next post, assuming this problem stone doesn’t give me any more issues…

Ok, so I’ve got a commission for a pair of 4mm pyrope garnets for a pair of earrings, and I need to us a specific sized dop. I look at my set and see that the dop I need already has a stone on it…

Then I remember why… this particular topaz I was cutting over a year ago and had nothing but trouble with it, and only got the pavilion partially done. Issues I had with this stone:

• difficult design
• popped off the dop, and had to reset and recut
• started the recut and noticed an inclusion in the center I hadn’t seen before

So, I decided I’m going to recut this with a simple design and finish it regardless of the inclusion.

Got the pavilion cut and polished, started the crown… popped off the dop. FML.

I reset and glued the stone back on, and stepped away for a few days to ignore it and regain my patience. 😉

I’m going to see how this turns out and will post here when it’s done. Wish me luck….

What equipment do you use? What kind of laps? What’s your go to for dopping a stone?

As a reminder this is the design being cut:

Once the glue was set I removed the old dop and placed the new dop in the cutting head. This is what it looks like before I get started on the crown.

What will take the longest on the crown is sizing the girdle by cutting down the stone. What I like to do is do this across three facets to speed up the process. In this cut I'll first cut index 96, then 12, then 84. Then I'll go back to 96, 12 then 84. I'll keep doing this to bring the girdle to the desired thickness.

I get pretty close to what I want here:

So I then cut the remaining indexes.

Next I changed to my pre-polish 3000 lap, and pre-polished the first tier to get the alignment as perfect as I could. Then I cut the remaining tiers of the crown with the exception of the table.

Then I polished the crown tiers, minus the table which hasn't been cut yet.

(picture is blurry as the phone just can't seem to focus on the polished facets up close)

The table is the last facet I'll cut and polish. I take the dop out of the cutting head and attach the 45 degree adapter. This allows for a precise table.

Table is cut, and just needs to be polished.

Lets look at the render again:

Here is the final stone, under a lamp inside.

Outside in the sunlight

In a box with backing inside.

As you can see you get different light return based on the kind of light and how the stone is held. In the last image you can just see what the render was showing.

I've enjoyed sharing how I cut stones, feel free to ask any questions.

Thanks!!

As a reminder here is the diagram of the cut being done.

We left off last time with a mistake that needed to be corrected. I over cut the final tier on the first facet. So I decided to switch to my pre-polish lap the 3000 grit, and pre-polish the girdle.

Then I recut the tiers using the pre-polish 3000 lap.

2nd Tier:

3rd Tier:

4th and 5th Tiers:

For polish I use a tin lap that has had 60k diamond paste applied. I run this at a low speed and use a spray bottle instead of the drip tank for lubrication.

Polishing goes very fast, only a few swipes across the lap and a facet is done. Here are the 2nd and 3rd tiers polished.

Finally the pavilion is polished. My apologies for the blurry picture but my phone just can't seem to focus on the polished surface all that well up close.

Now that the pavilion is complete, I need to transfer the stone to another dop in order to cut the other half. I do this with the transfer jig. I place the current dop in making sure that the angled piece if firmly against the slide. This is allows both dops to be aligned at the index level.

At this point I'll carefully push the new dop up against the stone. Notice that the new dop has a concave surface to better hold the pavilion. Then I'll glue the stone to the new dop and let that set.

Next time I'll start on the crown of the stone.

Now it's time to finish cutting the remaining tiers in the pavilion. Here is the diagram I'm cutting:

First thing I'm going to do is switch my lap to 1200 grit and recut the existing girdle and first tier facets. I'm doing this because the 1200 is more accurate and I want to get the cuts close to their final depths.

This is the result, can you see the issue?

There is a fracture in the stone right around where the girdle and facet meet, the shiny spot. The issue with this is two fold:

1. The stone will have a visible imperfection when finished
2. This is a weakness that may chip off the stone in the future.

So, I need to cut that out. What I need to do is reset to 90 degrees and cut that facet's depth down until the imperfection is removed.

While I was doing this I heard a crack sound, pulled up the stone and saw that the fracture had broken, and now I have a divot in the stone where it used to be.

So, keep cutting until it's gone

You can see in the above picture that the divot is gone, and the girdle facet is larger than its neighbors. Time to finish cutting the remaining girdle facets to match, and recut the second tier.

Before:

After:

Now I set my angle to 47 degrees and cut the next tier:

The first of the defined triangular facets appear. Something to note, when cutting we try and make the meet points as perfect as we can. A meet point is where the tips of the triangles meet. In this case the tip of the triangle meets the joining point of two girdle facets.

Onward to 41 degrees and the next tier.

So, even though the first second tier is now triangles, the third is going to end up being parallelograms.

Last tier using 39 degrees.

Ok... so I made a mistake here. I outlined the facets with an aluminum pencil to make it easier to see the issue. I didn't realize that this last tier was going to cut as fast as it did, and I over cut the first facet of the tier.

Good news: I can go back to the second tier at 55 degrees and recut those facets, then iterate back through the other tiers.

Bad news: I have to recut all of those facets again.

Next time I'll have the pavilion cut and polished and ready for transfer.

Lets look at the design again:

I always start on the pavilion tiers, and the first step is to cut in the girdle. When I roughed the stone into a cylinder it wasn't going to be perfect, so what I do is set my angle to 90 degrees and iterate through each index (96, 12, 24, 36, 48, 60, 72, 84) until I find the one index that is the deepest. That is if I set the stone at index 96 and increase the depth such that the angle hits 90.02, and the next index reverts to 90, I'll increase the depth until the angle reads 90.02. This finds the location on the stone that needs the least cut off, and is the starting point for cutting in the girdle.

To cut the girdle I'll increase the depth to something like 90.20 and cut until I reach 90.00 again. If the facet looks like it is even and takes up enough space of the circumference then I'll move to the next index and leave the depth alone. Once I've cut the girdle in it looks like this:

Once the girdle was finished I noticed that I had a much longer cylinder than needed for the width. I checked the design in the CAD software to see what the total height of the stone will be given the 9mm width.

I measured the height and decided that I could get two stones out of this piece, so measured and marked a cut.

I changed to my saw attachment and cut off the top to be saved and used for another day.

Next I set my angle to the next tier of 55 degrees and cut in the next tier.

Once done, the rough in looks like this:

At this point everything I've done is not very accurate and really rough, and I'm fine with that. The whole point of this stage is to remove most of the material in preparation for the higher precision work.

In the next post I'll be fine tuning the first two tiers and cutting in the remaining pavilion tiers.

This is the first post in a series that will try and go into detail around how I cut stones.

In general you don't start with a design you start with the stone. I chose a stone that was large enough that it would be easy to take pictures of the details as I cut. For this I chose this piece of clear Topaz. Many people know Topaz in a variety of blue hues, but in reality most of those blues are not natural. To make a stone blue, the stone is irradiated which turns it brown. Then the stone is heated to 500 degrees or higher for a period of time which then turns the stone blue. The actual hue of blue depends on the amount of time the stone was irradiated and/or heated.

This particular stone has a piece off to the side that is full of internal cracks and inclusions. Ignoring that portion, there are additional issues with the stone on two corners. In looking at the stone as a whole, it looks like I can get two rounds out of the stone by making the following cuts.

To make these cuts I'll use a saw blade attachment on my machine:

First cut off the side piece:

Next cut it in sort of half, and you end up with these pieces:

The upper right and bottom are the two pieces that can be cut. The upper left is unusable due to the internal issues it has.

The next step is to hand rough in one of the two stones into a cylinder.

Which now looks like this:

Finally, I glue the stone to a dop, and it's ready to be put in the cutting head.

Now that I have the stone roughed in, and on a dop, what kind of design am I going to cut? I chose the following design I made a while back but never cut which I call 'spinning top'.

It's render from the cad software I use looks like this if you are looking straight down into the stone.

Well, we shall see what it really looks like when we are done!

I'll continue the process in the next post.

I was asked by a lemmy user to write up a summary of how stones are cut. This post is my attempt at sharing what I know and how I cut. I do this as a hobby and am by no means an expert, so I'm sure there are techniques and such that I don't cover.

Designs

You can't cut a stone without a design of some kind.

A cut stone is typically divided in two halves: pavilion (bottom) and crown (top). Each half has a set of tiers that that are differentiated by the angle they are cut. In the design above there are three tiers in the pavilion and four tiers in the crown. Within each tier each facet is defined by the index, a number that indicates a position around the circumference of the stone.

The angle for each tier is important to the overall stone's color and light return due to each type of stone's R.I. (refractive index) value. The refractive index indicates the deflection light takes when it enters the stone.

In the past many designs were done by hand using math, but these days there is great cad software that allows a cutter to create their own unique designs.

Even with the CAD software, there is still the need to understand a great deal about how light interacts with a stone to achieve that perfect design.

Cutting Machine

There are three major types of cutting machines: mast, hand piece and jam peg. In this post I'm only going to cover the mast type, as that's what I use.

Mast

The mast allows for fine adjustment of the depth of the cut using the knob and wheel at the top. This control moves the cutting head up or down against the cutting surface.

Cutting Head

The cutting head holds the stone and allows for two different positional adjustments.

Index

The index of the stone is the position around the circumference of the stone as defined by the index gear.

There are additional index gears that can be put on the machine with the highest running 120 index positions.

Angle

The cutting head can be adjusted to specific angles as defined by the design. For this machine, the accuracy of the angle is 0.01 degrees.

Base

The base of the machine contains the motor, speed controls, splash guard and water drip tank.

Additional Equipment

Dops

A dop is a brass rod that stone is attached to, either by glue or wax, and fits into the cutting head.

Waxed on stone

Glued on stone

Laps

A lap is the actual cutting surface that fits onto the spindle on the machine's base.

Laps come in a variety of grits: 260, 600, 1200, 3000 (pre-polish) etc. For polish I use a 60,000 grit diamond paste on a tin lap. When working with laps, cross contamination of laps from lower to higher grits can cause scratches when trying to pre-polish or polish, so keeping them clean is important.

The Cutting Process

Rough Stones

First things first, I pick out a piece of rough and look at it closely.

In the above image, the rough from left to right are:

• Amethyst
• Montana Sapphire (Yes Montana has sapphires!)
• Topaz
• Apatite
• Morganite (nice peach color)

What I do is look at the existing shape of the rough as well as any inclusions or fractures within the stone in order to attempt to determine the shape I'll cut the stone into in order to maximize the yield. Generally a cutter will lose 50% (less likely) to 60% or more of the original stone.

Pre-form or Rough in

This step is all about creating the rough shape of the stone. For example, if I am going to create a round stone I'll form the stone into a rough cylinder using my hands against the lowest grit lap spinning at a moderate speed. I may also use a saw attachment to slice off a portion if the optimal usage of the original material dictates I can save and use it. Additionally I may hand rough in a general pavilion shape to speed up the cutting process later.

The final step is to flatten one end of the cylinder to act as a starting point for the table (flat top facet on the crown). This serves two purposes:

1. Clean point to glue to the dop
2. If the stone pops off the dop during cutting it can be realigned vertically using that same surface.

Attaching the Stone to a Dop

What I use for gluing a stone to a dop has changed over the years. I used to use a very hard wax that I would heat up and attach to the dop and stone. I still do this for smaller stones, as it provides me the ability to readjust the stone on the dop until I'm happy with it. For medium and larger stones I use super glue and have gotten pretty good at aligning the stone quickly before the glue hardens.

Cutting the stone

I was going to describe how I would cut the above design, but instead what I'm going to do is start a new stone from scratch. I'll post a series of posts with images and descriptions of the steps I'm performing to give all of you a good idea of the entire process I use from start to finish.

This is a pyrope garnet set in sterling silver. She did pretty well on this, with only a few mistakes here and there.

Since there was some discussion around cutting, I thought I’d post some pics I took during the cutting of the previously posted iris cut.

So roughed in the pavilion and cut the girdle and first tier.

Next, finish cutting but not polished the pavilion.

Pavilion polished

Next step is to transfer the stone to another dop to cut the other side.

Cut the crown of the stone without polish or the table.

Polished crown without the table

And now the final result

Feel free to ask questions!

cross-posted from: https://lemmy.world/post/86605

I cut gemstones and cut this in a custom design, and wanted to share with Star Wars fans.

These are all either practice stones, some of my most precious or stones I've done just for fun. I've cut for friends, family and commission but keep it more of a hobby than a business. (No I'm not soliciting for work.)

The types of stones in the image are:

• quartz
• amethyst
• tourmaline
• beryl (both golden and aquamarine)
• garnet (mostly pyrope)
• topaz
• sapphire

I'll keep posting as I have time in hopes that there are some lurking lapidaries out there that will eventually chime in. 😀

Ultratec V5, old mac book pro to run gem cad studio, and a custom built cabinet to hold supplies. I really love the pull out shelves for laps, dops and other supplies.

I have a real hack around dealing with splashes while cutting the girdle. Notice the backing cover which is some cardboard wrapped in plastic shelf liner. Avoids those splatters against the wall, shades etc. And yes.. that is a kitty litter container under the desk to capture the water.

This is a new design that has 198 facets that I thought was going to be a challenge to cut, but was much easier than I anticipated. I would have uploaded a video, but haven’t figured out quite how to do that yet.

In the past I used a Graves mast and the cutting head used doos with a tiny hole and brass rod to align the dop to the index. This worked really well on transfer to align both dops.

Now with my ultratec I swear I have yet to get a properly aligned index on transfer with their transfer jig. I have to always test a polish on a girdle facet and use the cheater to re-align the index.

Anyone have any tips?

I was trying something new with a hex shape, but didn’t quite get the desired light play. I think it looks more like a flower, may have to change the name. 😂