Thanks for your responses. Could be another uranium mineral or meta-autunite. I have handled a lot of these through the years and seen a lot of hyalite and autunite in larger crystals, crusts, etc. Maybe I should have been clearer. However, I'm betting big time on autunite/meta-autunite based on a lot of experience. You can see the color and crusty/smear habit most often displayed by autunite in pegmatite material. Secondly, does not fit any description of hyalite except it fluoresces green and certainly appears to be misidentified as hyalite. And diagnosing hyalite because the stuff fluoresces green just does not work for me. Fluorescence is not an intrinsic enough property to depend on for identification purposes.  Helpful, yes. Diagnostic, no. These are not large grains of material so it is difficult to see with just a 10X loupe. There is no sigh of typical bubbly hyalite but I would want to get these things under a better microscope before I say there is no hyalite at all in these specimens. So, for sake of argument, let's just consider them either "autunite" or "hyalite" as a reasonable field identification. We can deal with what uranium mineral these might be later. The specimens in question go back 50 years just before I hit college. I took other collectors word for many things. Years later, I know what to look for to separate out "hyalite" and "autunite". I am an experienced crystallographer. Just ask Don Peck. So, not workable crystals, just crusts. And no uraninite seen in the specimens.  What I was most interested in was the probability a lot of material; like this has just been called hyalite for a number of reasons but mostly because it was just plain easy. A lot of amateurs don't have the knowledge or skill to separate out some of  these situations. As Harold noted, autunite is typically scattered about. As to color, you have to get right into the face of these tiny grains to see the giveaway color. So, quick flash of UV and you have hyalite. And that doesn't work. Quick flash of yellow crust and that says "autunite' as a good starter to separate the two.

What brought this whole double checking was I wanted to see what the latest insights and information was regarding the uranyl ion in hyalite. So, I started pulling specimens in the collection. First thing I noticed was some misidentifications from many years ago.  The uranyl ion  story is much more complex with the presence of possible uranyl phosphates and uranyl silicates. Too many seem to have the impression that the uranyl ion is just somehow floating around in the hyalite. The uranyl ion is intrinsic to some of the minerals now known to be in the hyalite and those included minerals are fluorescing.  So, again, I was just wonder just how much misidentified material is out there. I think there is a lot.

Best Regards,

Al 

Best Regards,

Al

I have access to various useful but nonspecific tools, and they just make it easier to know that my labels are wrong, but not good enough to know what would be right. I have a blue fluorescing mineral that I would otherwise have thought was margarosanite, but the XRF says it isn't. I have a green fluorescent mineral that I might have thought was due to uranyl ions, but no radiation or uranium. I have a specimen sold to me as silver and acanthite, but it turned out to be full of arsenic (so safflorite, which pictures later proved to be almost surely correct). I have an anterite that turned out to be atacamite. 

Sometimes the tools help, but often they just remind me that the natural world is complicated and there is a lot more going on in most specimens than I could ever put on a label.

Peter Megaw hinted at this on articles about the electric opal from Zacatecas. There is more information in this article.

 The uranyl ion is intrinsic to some uranyl phosphates and silicates and fluorescence is intrinsic to the minerals. So, a mineral disseminated in the opal is fluorescing, apparently due to the uranyl ion in the mineral but it is not just the uranyl ion floating about some how. Ions don't really do that. They bond. And if the uranyl ion somehow coordinates itself with the silica or with other minerals, it really isn't just uranyl anymore, it is a new mineral. And that is where the uranyl phosphates and silicates may well come into play. And a lot of times, a green fluorescing film across a specimen is just considered hyalite for no other reason than it must be. That just does not satisfy my curiosity.  Check the link I just posted to Herwig. Lots of info on the mentioned minerals and their possible roles in fluorescent opal. 

You are so right about the complications we come across in nature. But I have spent about 75% of my life asking questions pertaining to things geologic. I could easily have become a professional student. So, I spent a lot of necessary time in the classroom but headed for the rockpiles as fast as I could. Labels are only meant to be a brief introduction to the story of a specimen. Too many rocks. Billions of years worth and I have only a short human lifetime... Still, I want to know.

Best Regards,

Al

Doug