The Largest Faceted Hyalite Opal

 

Steve Moriarty has just finished the largest faceted Hyalite Opal ever. You can see the completed gemstone here.

 

Video Transcription

 

I'm Steve Moriarty from Moriarty's Gem Art. We're a jeweler on the square in Crown Point, Indiana. We're also represented online as moregems.com. Today, we're here Chris Clemens, and he is the president of the Midwest Chapter of the Fluorescent Mineral Society. He's going to explain what we're going to be doing today.

 

Thanks Steve. Today, Steve's going to be working with a very unique and unusual gemstone material, called hyalite opal. This particular material is from Zacatecas, Mexico. Like all opal, hyalite opal is composed of silica primarily. Hyalite gets its name from its bubbly glass-like appearance. Hyalite is a word that means glass-like. But it has a couple of very interesting and unique physical properties that I'd like to talk about.

 

First and foremost, there's a property of fluorescence under ultraviolet light. If we light this piece up with long-wave ultraviolet, you can see that it fluoresces or glows very brightly, kind of a yellow-green fluorescence.

 

The second property that I'd like to talk about relates to the reason that this material is fluorescent. Hyalite acquires a property of fluorescence due to the inclusion of trace amounts of contaminating uranium in the silica structure of the opal itself, and under ultraviolet light uranium will glow very brightly, creating that brilliant fluorescence.

 

As you probably know, uranium is an element that's also radioactive, so the other property that I'd like to talk about is radioactivity. We can actually measure that with this device. This is called a Geiger counter, and it measures radioactivity. If I take the Geiger counter probe and hold it near the specimen, you can actually hear the measure of the radioactivity being emitted by the opal in terms of the pings that the Geiger counter gives off. As radioactivity goes, this isn't what you would consider to be terribly hot material. It's not very radioactive, but radioactive nonetheless.

 

Again, it's the presence of that radioactive uranium in the opal structure that causes the fluorescent response under ultraviolet light. This is a piece of specimen quality hyalite opal that would make a nice display piece in somebody's rock and mineral collection. Steve's actually going to be working with a piece of facet rough of the same material, from which he's going to create a beautiful hyalite opal gemstone that will have the properties of fluorescence, as well as low levels of radioactivity.

 

This piece of rough, it actually weighs about 25 carat. I've looked online to see what's available, and I see stones cut maybe as big as three carat, but this is probably going to cut over 10 carat, maybe a 15 carat gem. To do that I had a couple of choices, whether to cut an oval or cut the basic shape it is, which is kind of like a half moon. I'm going to go for the weight, which is the half moon, because this material is not particularly brilliant anyway, so I'm not really after brilliance. I'm just going after the unique shape that it has and getting as big a gem as possible.

 

What really attracted me about this material, yes it's fluorescent and it is beautiful fluorescence, but the really unique character of this fluorescent gem is that even in daylight, particularly in the Summer months or Spring and Fall, it fluoresces just with sunlight. And I don't know, is there any other material that does that?

 

Not too many. Some fluorescent minerals will display a property called daylight fluorescence, and that's what you're describing Steve. By which you can actually take the material outside and under the rays of sunlight, which contain as everybody knows some proportion of ultraviolet light, that will actually cause it to glow that greenish yellow color actually outdoors. So you don't necessarily need a special ultraviolet lamp, like we have here, to see the fluorescence. You can take it outside and actually see it fluoresce under the daylight.

 

Which is cool. I tried to show that recently, and in the Winter months there's so much less UV. It barely fluoresced. Whereas in the Fall, I had it out there and it was maybe half of what this light does. We really had a beautiful fluorescence.

 

Yeah, there are a handful of minerals out there that display the property of daylight fluorescence, and hyalite opal is one of the more notable examples.

 

We're ready to start cutting this hyalite opal. As I had mentioned we're going to try and do a step cut kind of a shield, or it will be almost like a half-moon. Get it in the machine, and as Chris mentioned, this material is radioactive, so we're going to take some extra precautions during cutting and wear a mask to try and prevent any inhalation. My video photographer Mike is also wearing a mask. If I can get it on.

 

The other thing we're going to do is run a lot more water than I normally would. This should prevent any dust getting into the air. Just a good steady stream.

 

So here's our finished hyalite opal. It finished out at seven carat 7.27 carat. It's got a à propos that the ideal shape for greatest yield ended up being a Superman shied shape. À propos because it is radioactive, and it also has the green glow of kryptonite.

 

So as I stated earlier, the unique character about this, not only does it fluoresce under ultraviolet light, it also fluoresces in daylight, which we'll show you now.

 

Even in the Winter, which is very low UV because the sun's so low, it does still take on characteristic green glow. So you don't have to carry around a UV light to see the green that this fine hyalite material shows us.