I Facet A Stone That I Found In The Desert, But What Is It?

Hello and welcome to Matt's Corner of Gem Cutting. Recently I found some interesting stones out in the desert. I picked out this piece to facet in this video. I'm not 100% certain on what the stones are, but they are fairly transparent and some are suitable for faceting. The stones tend to fluoresce green under a black light. There is a lot of what looks like crazing on the outer surface of the stone. I think this might be due to sitting out in the sun for a very long time. I found these stones by searching an area near where my mother-in-law, Holly Remkes, who does a bit of exploration, had found a stone that ended up fluorescing green. While searching, I came across some bubbly opaque white stones that caught my eye. When I bent down to examine them, I noticed some of these translucent stones in the dirt in the same area. I would likely have missed these pieces walking around in the daylight if those white stones didn't catch my attention. I believe the white stones are white opal and could possibly be connected with the translucent stones that I was finding. Once it got dark, it was a lot easier to find anything that fluoresced green while walking around with the strong black light. The fluorescent stones lit up really bright. I was using a longwave UV light, but the stones fluoresce under a shortwave light as well. I walked around for a while after dark and picked up whatever pieces I could find. I had to be a little cautious though, as the stones weren't the only thing out there that fluoresced green. There were plenty of scorpions around, and they fluoresce just as well as the stones do. Here are some of the pieces that I was able to find, with the one that I will be faceting right here in the front. Some pieces fluoresce more or less than others. It seems like the pieces with a little more color tend to fluoresce better. This is the first piece that I picked up. This one has a very bubbly look. Some are like this, some are a single roundish piece, and some are a little more flat. But the pieces all have these lines that make me think that the stones formed by layers building up on each other. The green fluorescence is most likely caused by trace amounts of uranium in the stone. This piece has really good fluorescence, and you can see some small round white mineral inclusions along the break on this edge. Some of the pieces have some of these inclusions internally. The stone happened to break where some were, which makes it easy to show them. This is a pretty cool piece that I found. It looks a lot like an alien head from the side profile. This large piece is kind of flat looking, but it still has those distinct layer lines. It does get a little more rounded on its one edge. Now back to the piece that I will be faceting. It comes to a point on one side, which I will use as the culet of the stone. If I do that, the crown portion is already very domed-like, so I want to do a cut with a high dome to best use the current shape of the rough piece. After roughly a couple hours of failing to create a design that I liked, I decided to just get on the Gemology Project website and pick out a cut from there. I like the general look of Arya Akhavan's Tessellation 9b, so I decided to go with it. I opened the design in GemCut Studio so that I could make the crown deeper and optimize the cut for the stone that I am working with. I found that the refractive index value of these stones is about 1.47, which is a lower value as far as gemstones go. I can check the rendering of the design at different Ri values to check the estimated outcomes of the faceted stone. The refractive index value is for how much light bends when passing through a material. The Ri is currently set for 1.54, which is the refractive index of quartz. The design becomes more brilliant when adjusting for stones with higher Ri values, stopping at 1.76, which is the Ri for sapphire. The design looks really great, but as I adjust down to the Ri value for the stone I will be cutting, the design loses a lot of its liveliness and seems more dull. So I use the optimizer tool, while set to the Ri value of 1.47, to adjust the crown and pavilion depths of this design. I end up with a deeper, more domed-like crown and actually shallowed the pavilion some. The end result will produce a little windowing in the center of the design, but should overall increase the liveliness of the stone. Keeping the pavilion deep enough to not window towards the center of the design would leave most of the outer portion of the stone lifeless, and any shallower would produce too much windowing towards the center. So the optimizer tool helped me find the sweet spot for working with this stone with a lower Ri value to still achieve a good amount of brilliance. This is how the design looks now. The design is the same, other than all the facet angles are different. His original design, which can be found on the gemology project, looks great for most stones with an Ri value of roughly 1.54 or higher. My edit was to specifically optimize the design for this stone. The Ri value of 1.47 leads me to believe that the stone could be opal or some type of glass. There are types of both opal and glass that fluoresce green. There are a lot of variations of glass, whether natural formed or man-made, that can cover a very wide range on the refractive index scale, from about 1.44 to 1.9. Opals tend to range from 1.37 to 1.52. There are some other stones that fall in the range, but don't seem likely based on their crystal structure, color, and other properties. The refractive index of this stone is very close to that of Libyan desert glass, which is believed to be formed from a meteorite around 29 million years ago. The theory is that large aerial bursts from a meteorite cause radiative melting of sand on the earth's surface forming the glass. Although the glass itself isn't of cosmic origin, it would be really neat if these pieces were formed similarly from a meteorite, as with its fluorescent screen property, it would make it very kryptonite-like. Though, I don't think it is very likely that the stones that I found were formed from a meteorite. I haven't found any images of stones that look exactly like what I found, but they really don't resemble meteorite-formed glasses. Libyan glass and meteor melt glasses mostly look like melted glass. Here is a tektite that is formed from a meteor. It is hard to see, but it has some transparency and is also a form of glass. Sometimes, a meteor impact will eject molten material that cools while flying through the air, forming oblong, somewhat raindrop-like shapes, and has a surface texture similar to that of meteorites. This is also very different from how the pieces I found look. Moldavite is a tektite that is formed this way and is classified as a gemstone. It has a dark green color and decent transparency, so it is commonly faceted and used in jewelry. Now, a more down-to-earth possibility is that the pieces could be slag glass left as a byproduct from old uranium mining and smelting. Sand is often used as a heat buffer when working with molten metals. The sand can melt into glass and be left as a byproduct. Slag glass from uranium mining can contain uranium, giving it that distinct green fluorescent glow. Though this is a possibility for these pieces, I'm still not so sure that is the case either. Any images I could find for uranium slag glass seem to be fairly opaque and again don't very well resemble the pieces that I found, though I don't know if that is enough to fully rule out the possibility. This piece of slag isn't from uranium mining, but large pieces of slag glass like this are often for sale at rock shops. A lot of slag like this is produced from ore refining and can be various colors. Perhaps the rocks I found could be a glass that formed naturally in some other way, although I don't have any other insight into what could have caused the formation. Obsidian, for example, is a natural formed glass, but obsidian doesn't seem much like what I have found either. So, onto the possibility that these pieces could be opal. I think that this could be the most likely based off my findings, though still not conclusive. There is a type of opal that is known to have green fluorescents called highlight opal and sometimes called bubble opal because of its bubbly looking formation. Highlight has been found in quite a few locations around the world, including Utah, so it is possible that this could be a common opal similar or even a variety of highlight opal. Common opals differ from precious opals in that they lack those vibrant plays of color that are typically associated with opal. Some of the better highlight opal specimens seem to be coming from localities in Mexico. I picked up a specimen at a rock show for examination and also acquired some faceted highlight pieces. The specimen's formation looks quite a bit different than my pieces, but there are some layer looking lines on the specimen that look similar to the ones my pieces have. The specimen only shows weak fluorescence under a short wave UV light, while the faceted pieces fluoresce under both a short wave and long wave UV light, though they do fluoresce better under the short wave. There is some curvature bands that can be seen in this one faceted piece while it is fluorescing that also looks a lot like what my pieces are doing. My pieces fluoresce pretty well under both the long and short wave lights. Highlight opal is sometimes referred to as kryptonite because of the green fluorescence, but it would be a lot cooler if it were an actual space rock. Most highlight opal tends to be clear, whereas my stones are a pale yellow in color, though the highlights that are daylight fluorescent tend to have a slight yellowish green hue. The pale yellow color does fall into the range of colors for another type of common opal called fire opal. Fire opal gets its name from the fiery reddish orange hues it can come in, though the pieces I found lack in rich vibrant color, they make up for it with that cool green fluorescence they exhibit. Though some fire opals are said to fluoresce, a quick search didn't return any images of fire opal fluorescing. So if these stones are opal, would they be more of a highlight or fire opal? Or perhaps somewhere in between? If that were the case and these pieces do turn out to be opal, maybe I'll make a play off both types of opal and call it firelight opal. I'll send the finished piece to GIA to see what they have to say about the piece, and maybe additional testing elsewhere if needed. So hopefully I will be able to confirm what these pieces are in a future video. This stone doesn't seem to have a really high hardness. Both glass and opal have a similar hardness with a range between about 5 to 6.5 on the Mohs hardness scale. That is a little on the softer end for gemstones. Stones with lower hardness are prone to scratching and receiving wear easier than harder stones. So when softer stones like this are put into jewelry, protective settings are recommended to help protect the stone from rubbing on other surfaces. The faceting of this stone is now winding down as I finish up the polish of the crown facets using cerium oxide. The stone polishes fairly quickly using cerium oxide, which also indicates that its hardness is less than 7, which is roughly the hardness of the polished compound. A quick cut and polish of the small table facet is all that is left to finish off the faceting of this stone. This stone was a bit rough looking starting out, with all the micro fractures and discoloration it had on its surface. That was kind of neat in its own way. I'm sure some people will say they liked it the way it looked before. But working the stone revealed a crisp and clean interior that was transformed into a beautiful gemstone that the piece had potential to become. When the black light is held over the stone, some little rays form going into the stone from the edge of the facets that reminds me of rays of sunlight shining down into a body of water. I didn't know that there would be these rays, so that was a fun surprise. Here is the finished piece. It started out at about 50 carats and is now 13.2. A very interesting piece with the triangle trillion-like symmetry. I think that the cut suits the stone well. The modification to the design turned out pretty good. It fluoresces such a nice green. Rotating the stone in my hand under a black light is quite mesmerizing. The stone has so much character that is brought out by the hidden fluorescent property. I mean, it is still a decent stone without it, but that fluorescence is something else. Looking at the stone out in the sun, it does display daylight fluorescence, which is picking up a little of that green fluorescence in the sunlight. I really like this piece. It is a really fun one for being something that I was able to find out in the desert not too far from where I live. Let me know in the comments what you think of the stone or what you think it might be. Even with all the research that I've done, I still don't know for sure, but whatever it is, it is pretty neat. Thanks for watching.