gemfeller
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Post by gemfeller on Mar 26, 2020 19:16:31 GMT -5
gemfeller Thanks for the links. Both articles are very interesting. Did you see the picture of the garnet crystal I cut in half? Garnets are pretty crazy the way their asterism presents. Glad you liked the links. I contributed some unusual 4-ray smoky/citrine star quartzes that are illustrated in the Nordskip link. There was an interesting discussion about them on Gemologyonline that I'll try to link if you're interested. Don't recall seeing the image you reference. I have a copy of the Lithographie LLC book "Garnet - Great Balls of Fire." It has a great section on how asterism in Idaho star garnets is arranged. And somewhere in my cluttered files I have a rare paper written by Dudley Stewart who founded Stewart's Gem Shop in Boise ID, showing how stars relate to crystal symmetry. Dudley was basically responsible for popularizing Idaho star garnets as you know. I'll post it when/if I can find it. Since you're a star garnet aficionado you might want to pick up a copy of the Lithographie book. I think it's still in print. |
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gemfeller
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Post by gemfeller on Mar 26, 2020 19:21:33 GMT -5
dreamrocks, I tried using Star Refractol on several pieces of rough quartz I know will star, but no luck -- so far. It was a quick-and-dirty test and I'll try again. I may try a tiny drop of honey next. Lack of results may be due to the fact that star rose quartz usually displays epiasterism: stars show only via transmitted light, not reflected light as with star sapphire etc.(diasterism). That's probably why they're so hard to photograph. Another problem is not every piece will have a star or eye. Its like comparing rocks that fluoresce from the same location some do and some don’t True, but I was testing a piece of rough I KNOW will star. I even tested a tumble-polished piece with a visible ray but no luck -- so far. |
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Deleted
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Post by Deleted on Mar 26, 2020 20:11:22 GMT -5
True, but I was testing a piece of rough I KNOW will star. I even tested a tumble-polished piece with a visible ray but no luck -- so far. I haven't had much luck with the drop of oil or honey techniques. The only time even a hint of chatoyancy, let alone a star, was in direct, midsummer sunlight. Might work better on some materials than others, but I mostly have tried with garnets, where people claim this is foolproof. Signed, a fool. |
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gemfeller
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Post by gemfeller on Mar 26, 2020 20:36:10 GMT -5
dreamrocks , I've owned a GIA Gem Instruments polariscope since the 1980s but haven't had consistent luck finding the C-axis in rough rose quartz. It's massive, not crystalline, so there's no obvious place to look though I've been able to do it occasionally. There's lots of turning, twisting and neck-craning involved in locating and marking the right spot. Most of my rough is too large to easily manipulate between the polars of my instrument. I'd try again tonight to see if I can come up with a better technique but my wife fell about 10 days ago and seriously fractured her ankle. So for the next 4 to 6 weeks I'll be doing all the "house duties" as well as taking care of her. And speaking of that, it's time to rattle some pots to make dinner.
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dreamrocks
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Post by dreamrocks on Mar 26, 2020 20:52:32 GMT -5
That’s good to know I was thinking of getting one but will hold off.
Do you have any experience with using the spectroscope for checking gem rough that’s another toy I want to invest in. If so are they worth the investment I have read the hardest part is getting use to reading the scale but very useful in identifying some type of gem rough look a likes
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dreamrocks
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Post by dreamrocks on Mar 26, 2020 20:58:58 GMT -5
I think a lot of problems finding a star or eye is due to the size of the inclusions with rutile if they are very tiny it would be a faint to very pale star. I have tried using a loupe to find them but they are to fine even on a tumbled stone even if you could see a line as in a eye or ray as it turned out I wanted to know if it was possible to see with a loupe nope no go
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Post by knave on Mar 26, 2020 21:54:58 GMT -5
dreamrocks , I've owned a GIA Gem Instruments polariscope since the 1980s but haven't had consistent luck finding the C-axis in rough rose quartz. It's massive, not crystalline, so there's no obvious place to look though I've been able to do it occasionally. There's lots of turning, twisting and neck-craning involved in locating and marking the right spot. Most of my rough is too large to easily manipulate between the polars of my instrument. I'd try again tonight to see if I can come up with a better technique but my wife fell about 10 days ago and seriously fractured her ankle. So for the next 4 to 6 weeks I'll be doing all the "house duties" as well as taking care of her. And speaking of that, it's time to rattle some pots to make dinner. Sorry to hear it. Doesn’t sound good, hope she heals fully and in a reasonable time. Good on ya for pitching in. |
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Post by Starguy on Mar 26, 2020 21:55:02 GMT -5
gemfeller Here is an Idaho garnet cut roughly in half. You can see the silk that causes the asterism quite clearly. It is more concentrated near the center of the crystal. I hope your wife heals quickly. 
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gemfeller
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Post by gemfeller on Mar 26, 2020 22:30:14 GMT -5
Starguy some are like that. We used to crack them open along existing fracture lines in the crystals and cut from the inside-out. Others have 4 and 6-ray stars in an orderly arrangement that can be cut from the outside. They vary depending on where they were deposited near Emerald Creek. Sadly I think my chart of star locations is kaput. I found the document but the illustrations are missing. Probably the result of several Windows upgrades since I archived the document. At times, when I'm in the right mood, I write doggerel "poetry." It would make Keats, Yeats and other sensitive souls scream and run in circles. But I leave you (temporarily) with this: Twinkle, twinkle little star, How I wonder what you are. Corundum’s likeliest by far, Mogok ruby? Wunderbar! But you ain’t red, you little devil! Perhaps you’re just an old “spin-evel.” Maybe you could be rose quartz, Or even a Linde with “the Schwartz” (May the Schwartz be with you!) Or maybe not. Garnet, beryl, orthoclase – Man, I’m really on your case! Peridot? Not too likely, yet – I’ve seen some starry olivine! Hmmm…that last line doesn’t rhyme So this is just a waste of time. Sit down at your Beacon star And find those twinklers – wherever they are!
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gemfeller
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Post by gemfeller on Mar 26, 2020 22:55:21 GMT -5
That’s good to know I was thinking of getting one but will hold off. Do you have any experience with using the spectroscope for checking gem rough that’s another toy I want to invest in. If so are they worth the investment I have read the hardest part is getting use to reading the scale but very useful in identifying some type of gem rough look a likes Polariscopes are simple, cheap and easy to make yourself. You can use the lenses from an old pair of Polaroid sunglasses. Do a search on it. They can be very instructive if you're interested in learning gemology basics: distinguishing between single and double refractive stones (very important!), determining optic axes and optic character -- and much more. I can refer you to an excellent tutorial for using one. Re: spectroscopes. Yes, I've used one for about 20 years. Learning to read the scale is simply a matter of pattern recognition and there are some very helpful charts. The cheapest and best scope IMO (and in those of some important gemologists) is the OPL Teaching spectroscope or the smaller pocket-size model. Both are diffraction grating types and are much cheaper than the bench prism models. They're made in England by Orwin Products Ltd. It took me a while to "see" the lines but after a few practice sessions -- and the help of a couple of great books -- it all started making sense. They're enormously helpful in distinguishing between look-alike stones and open a vast new and exciting world of gem learning. Colin H. Winter, FGA, DGA invented and sells them and he's written an essential book with great illustrations: "OPL - A Student's Guide to Spectroscopy." It contains numerous charts that illustrate the typical absorption spectra of a wide range of gems. I can provide more info if you decide to go that route. |
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Post by MsAli on Mar 27, 2020 6:05:31 GMT -5
dreamrocks , I've owned a GIA Gem Instruments polariscope since the 1980s but haven't had consistent luck finding the C-axis in rough rose quartz. It's massive, not crystalline, so there's no obvious place to look though I've been able to do it occasionally. There's lots of turning, twisting and neck-craning involved in locating and marking the right spot. Most of my rough is too large to easily manipulate between the polars of my instrument. I'd try again tonight to see if I can come up with a better technique but . So for the next 4 to 6 weeks I'll be doing all the "house duties" as well as taking care of her. And speaking of that, it's time to rattle some pots to make dinner. So sorry that sucks! Hope she has a speedy recovery! |
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dreamrocks
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Post by dreamrocks on Mar 27, 2020 6:50:53 GMT -5
Yes gemfeller I would appreciate any information on gem equipment you my have and your recommendations for gem equipment I have read a number of your posts and do find them of interest to me. Sorry to here about your wife and wish her the best in a speedy recovery |
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Post by broseph82 on Mar 27, 2020 10:32:10 GMT -5
The Hogg Mine at LaGrange, GA is a well-known source for asteriated rose quartz. I have some lovely rough pieces from there. I've also found a fair number of tumbled rose quartzes that display asterism, some very nice ones. But I'm getting old and lazy and keep putting off locating the optic axes to orient them. Easy job but other projects seem to take priority. One of these days...if the Kung Flu doesn't get me. I didn’t know that about the Hogg Mine. It’s on my list of regional places I’d like to go. Have to bump it up the list now. Don’t believe everything you hear. It’s kind of a tall-tale with Hogg Mine. Supposedly they do have asterism in some of their stuff but nobody has been able to produce proof. |
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Post by Starguy on Mar 27, 2020 17:06:04 GMT -5
I have 5 Kg of star rose quartz spheres ordered. They’re 40-45 mm which is pretty big. I’ll post photos when they arrive. They should get here in the next day or two. They’re from Madagascar. 1dave do you know about the geology of Madagascar? That country has some interesting mineralization. It must be part of the African rift/valley province. Judging from the minerals supplied by that country, it must have an interesting mix of intrusive and extrusive igneous. Corundum, rose quartz and agates are typical rocks mined there. |
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Post by 1dave on Mar 27, 2020 18:01:57 GMT -5
I have 5 Kg of star rose quartz spheres ordered. They’re 40-45 mm which is pretty big. I’ll post photos when they arrive. They should get here in the next day or two. They’re from Madagascar. 1dave do you know about the geology of Madagascar? That country has some interesting mineralization. It must be part of the African rift/valley province. Judging from the minerals supplied by that country, it must have an interesting mix of intrusive and extrusive igneous. Corundum, rose quartz and agates are typical rocks mined there. It is a complicated area! Susanne Lomatch is researching it in trying to figure out Ocean Jasper. Wikipedia has some good info: en.wikipedia.org/wiki/Geology_of_Madagascar |
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Post by 1dave on Mar 27, 2020 18:17:20 GMT -5
That as good as I could take the font is pretty small I like to scan images in, then enlarge them with my Paint.net free program. |
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Post by Starguy on Mar 27, 2020 18:21:28 GMT -5
Thanks for the post 1dave as I thought, extremely complex geology with a wide range of basement rock and much more recent extrusive. I need to check what is going on there with plate tectonics. I have acquired pounds of corundum from there. I got a 3.5 lb corundum crystal that shows an extremely nice star. That indicates a high percentage of TiO2 although that’s not uncommon in crustal rock. I also received some very nice rose quartz which indicates some large pegmatites. In addition, I got some very nice banded agate which tells me semi-recent extrusive activity. This area may be my next big interest over the Colorado Plateau. i live in the land described by Harlan Bretz. Also fascinating! I appreciate your knowledge. You’re a good man and a great contributor. |
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gemfeller
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Post by gemfeller on Mar 27, 2020 18:39:29 GMT -5
Starguy , when you look at the plate tectonics history of Madagascar you'll discover something very interesting. Despite its current location it was once part of Sri Lanka. Both are gemstone powerhouses. It drifted clear across the Indian Ocean and is not geolgically related to Africa. Mada is a gemstone "factory" that keeps on producing. It's been under constant modern gem mining exploitation since the 1980s or so, with amazing deposits of gem corundum, green grossular garnet (Tsavorite), alexandrite, abundant quartzes and just about every other fine gem imaginable. You're lucky to have a good supplier connection there.
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Post by hummingbirdstones on Mar 27, 2020 21:00:21 GMT -5
Starguy some are like that. We used to crack them open along existing fracture lines in the crystals and cut from the inside-out. Others have 4 and 6-ray stars in an orderly arrangement that can be cut from the outside. They vary depending on where they were deposited near Emerald Creek. Sadly I think my chart of star locations is kaput. I found the document but the illustrations are missing. Probably the result of several Windows upgrades since I archived the document. At times, when I'm in the right mood, I write doggerel "poetry." It would make Keats, Yeats and other sensitive souls scream and run in circles. But I leave you (temporarily) with this: Twinkle, twinkle little star, How I wonder what you are. Corundum’s likeliest by far, Mogok ruby? Wunderbar! But you ain’t red, you little devil! Perhaps you’re just an old “spin-evel.” Maybe you could be rose quartz, Or even a Linde with “the Schwartz” (May the Schwartz be with you!) Or maybe not. Garnet, beryl, orthoclase – Man, I’m really on your case! Peridot? Not too likely, yet – I’ve seen some starry olivine! Hmmm…that last line doesn’t rhyme So this is just a waste of time. Sit down at your Beacon star And find those twinklers – wherever they are! Rick, I loved your poem! Pretty good for off the cuff (except that 2nd to last verse LOL!).
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