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Identity HelpUnidentified Micros from Rhode Island

8th Nov 2009 02:46 UTCJonathan Woolley

Hello,

The recent addition of a microscope to my mineral hobby has me taking a fresh look at all the rocks I've acquired in the past. I was surprised to find both pink and orange microminerals on pieces of massive/microcrystalline fluorite I collected as a kid from a roadcut in North Kingstown, RI. The location was available only during the construction, and until now I was only aware of the fluorite (veins in a green schist matrix). I added the locality to mindat a few months back.

http://www.mindat.org/loc-209696.html

I'm not set up yet to photograph micros well, but I was able to get a few (somewhat blurry- sorry!) photos. I'm posting them here because I don't have a good idea where to start with micros, especially from a locality for which there are no references (as far as I know, no one else collected the site). I'm looking for suggestions on how to properly identify these as well as ID attempts if the photos allow for it. The orange crystals are all submillimeter size, and the largest of the pink mineral is about 1mm. What analyses can be used on something this small? If anyone can help, I'd be willing to part with a piece or two for ID.

The colors didn't come out extremely well, but the pink mineral is vivid pink and the orange mineral ranges from bright orange to a peachy color. The purple fluorite can be seen in the photos as well. First photo is of the pink mineral, other 2 are of different crystals of the orange mineral. Thanks!

8th Nov 2009 02:48 UTCJonathan Woolley

One more photo of a third crystal of the orange mineral.

8th Nov 2009 04:36 UTCMatt Neuzil Expert

possible sphalerite?

8th Nov 2009 04:51 UTCRob Woodside 🌟 Manager

Thanks for posting the loacality. This is the way that Mindat gets built. Any better idea of the geology than Fluorite veins in green schist. A macro photo of the veins might help. Sub millimeter xls can be analysed by x-ray diffraction or electron microprobe but will cost a few bucks. For now I see too many possibilities to be of much use.

8th Nov 2009 06:27 UTCJonathan Woolley

Hi Rob,

I checked out a geologic map of the area, and the fluorite occurance seems to be coincident with Triassic intrusive diabase dikes occurring along the major fault which separating the west side of the Pennsylvanian sedimentary rocks of the Narragansett Basin from granodiorites and alkali-feldspar granites of Devonian age. I would assume then that the schist host rock was probably created by metamorphism of the clastics during the Triassic intrusions, and I suspect the fluorite veins are secondary deposits in fractures along the fault zone.

Here are some larger photos of the host rock and veins. The vug on the right in the third photo is where the first photo of my original posting (the pink mineral) was taken.

8th Nov 2009 13:22 UTCUwe Ludwig

Coulor and XX-shape is like the Monazite-XX I found in the Austrian alps. However there matrix of my specimes is quit different. I recommen to check whether this phosphate of rare earth elements can be possible at this locality.

Uwe

25th Nov 2009 05:17 UTCMichael Kieron Expert

Hey Jonathan,

Nice find. The Jurassic dikes don't have much bearing on the schistosity of the rock, they are too low pressure to produce a foliated metamorphic rock. Your rock is part of the Scituate Igneous suite, which does have some local foliation. Fluorite is fairly abundant and REE minerals like monazite are common as well.

-Mike K.

25th Nov 2009 15:53 UTCsteven garza

Dear Jonathan;

I believe that you were at that rdct near I-295, where fluorite veins, some sphalerite, & some wulfenites were found. I think those are some of the wulfenites, which were blocky, rather than bladed xls & tended to be a bit 'eaten", bcs of decomposed sulphides (some galena was also found there). A good person to check with, is Nancy Millard (nancymillard.com). She's head of geology dept., at URI Knight Campus. say "hi" to her, from me, too!

Your friend, Steve

25th Nov 2009 16:35 UTCJonathan Woolley

Mike,

Thanks so much for chiming in - I was really hoping someone with more local knowledge of the area would find the thread. Are you in RI?

I'm working on getting some better photos of the different minerals soon. I would really like to get the pieces tested if I can find a good place. I'll keep the thread updated with whatever I can find out.

25th Nov 2009 16:55 UTCJonathan Woolley

Steve,

I will definitely check with Nancy Millard, thanks very much for the referral. However, the locality is the one thing I am sure of. The road cut was opened during the blasting to put in the southern end of Route 4. The coordinates which I entered for the mindat location are correct, but I double checked the map location and it is actually just north of the town line in East Greenwich. I have corrected that on the mindat locality page. Unfortunately, the exposure is gone - graded over when the highway construction was completed. I believe that URI has a few pieces from the locality which we donated at the time.

I would not be surprised if the orange mineral did turn out to be wulfenites, because some do have a similar look. I'm still very curious about the pink mineral - no suggestions on that one so far.

25th Nov 2009 17:22 UTCRob Woodside 🌟 Manager

Monazite? Does it change colour when illuminated in fluorescent or sunlight and in Tungsten light?

25th Nov 2009 18:19 UTCRonald John Gyllenhammer Expert

Zoisite (var: Thulite) ?

25th Nov 2009 20:29 UTCMichael Kieron Expert

HI Jonathan,

Yes, I'm in RI. I'm the assistant curator at the Museum of Natural History, Roger Williams Park. I get to play with ~12,000 rocks and minerals (when I'm not too busy). Is it marked by a couple small pieces of ledge a few yards from South Road? I was thinking that you are right in placing the road cut in EG since there is one of the EG Historic Cemeteries just south of South Road on the west side. I go down to URI regularly so I pass by it all the time.

Steven, Nancy is at CCRI, not URI. A little easier to find if you know the right school. Dr. Anne Veeger is the dept. head at URI.

Best,

Mike

25th Nov 2009 23:18 UTCJonathan Woolley

Hi Mike,

You have the right spot. If you're familiar with the area, it is almost directly west from Richard's Pub on Rt. 2 (Old Quaker Lane). During the construction they moved a lot of rock from between South Rd. and Stony Lane. Other than those few small ledges, I think the only remaining "outcrop" might be a few boulders that used line the back of Richard's Pub's parking lot. I don't even know if Richard's Pub is still there.

I'll have to stop by and see the collection next time I visit, since I never got to see it when I was growing up. I would be happy to donate a few pieces to the museum's collection if there is any interest. Not really display specimens (massive fluorites), but it might help preserve the locality information.

Rob, I'll check the color change if I can get a good tungsten light source for the microscope.

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