Re: radioactive tourmaline (dravite?)

Pavel Kartashov — Wed, 25 Nov 2009 18:47:15 +0000

It is normal situation, when Fe-rich members of some isomorphic series has more high IR than Mg-dominant members of the same series. If we see inverted situation, it means that Fe-dominant member with lower IR is very hydrated, metamict, has some specific admixture (F,Ti,Na etc.).

Mg rich host rocks for me are layers of dolomite marbles or serpentinites. :) 4% of MgO in biotite don't means that environment is Mg saturated, rather it means that the environment is Fe-rich.

Re: Green rock help please

Rob Woodside — Wed, 25 Nov 2009 18:26:04 +0000

Arghh!!! I misread Don's post. Amir, Thanks for the correction ::o

Sorry I missed the $1.00 betB)-

Re: Green rock help please

Amir C. Akhavan — Wed, 25 Nov 2009 18:20:08 +0000

Rob, the "formula" given by Don is the same as yours:
"Divide the weight in air by (the weight in air - the weight in water)"
M / (M-m)

I still stand by my one-dollar-bet B)-

Re: Unidentified Micros from Rhode Island

Ronald John Gyllenhammer — Wed, 25 Nov 2009 18:19:57 +0000

Zoisite (var: Thulite) ?

Re: radioactive tourmaline (dravite?)

Ronald John Gyllenhammer — Wed, 25 Nov 2009 18:14:22 +0000

Hi Jamey,

Thanks for the fact check. I stand by my statements as supported by the below listed sources.
______________________________________________________________________________

Source mindat.org:

Schorl, Uniaxial (-)
RI values: n_ω = 1.660 - 1.672 n_ε = 1.635 - 1.650
Maximum Birefringence: δ = 0.025

Dravite, Uniaxial (-)
RI values: n_ω = 1.634 - 1.661 n_ε = 1.612 - 1.632
Maximum Birefringence: δ = 0.022 - 0.029
______________________________________________________________________________

Source webmineral.com

Schorl, Optical Data: Uniaxial (-), Ncalc = 1.65 - 1.69, e=1.633-1.64, w=1.66-1.672, bire=0.0270-0.0320

Dravite, Optical Data: Uniaxial (-), Ncalc = 1.63 - 1.68, e=1.612-1.63, w=1.631-1.655, bire=0.0190-0.0250
______________________________________________________________________________

Citations for these sets of competent data can be found on the respective web sites.

Ron

Re: Small yellow sprays of unknown mineral from Poonah

Tomasz Praszkier — Wed, 25 Nov 2009 17:58:04 +0000

Sorry, of course I was thinking Nasik...

Tom

Re: Green rock help please

Amanda Hawkins — Wed, 25 Nov 2009 17:42:03 +0000

I think I'll have good night's sleep before I look at that ! >:D

Re: Green rock help please

Rob Woodside — Wed, 25 Nov 2009 17:32:08 +0000

Amanda!!! What could be simpler??? Two measurements- weight in air, M, and weight while submerged, m, both in gm. Then a subtraction and a division gives SG. Where did I lose you?.

Re: Locality problems after Intergem Antwerp 2009

Alain Hanson — Wed, 25 Nov 2009 17:27:31 +0000

Hi again Vik and Knut

I personally have small samples of heavily weathered arsenopyrite in clay and feldspars from the Kobokobo peg. with cyrtolite and U and Al phosphates collected in the sixties or the seventies by Van Wambeke. Similar samples are listed with METAFRO museum (sample 13098), (the link is [www.metafro.be])
Échantillon n ° 13098
Minerals found in the sample
Mineral ARSENOPYRITE SCORODITE
Description: massive block with green crust
Origin Country: Congo (RDC) Region: Kivu Locality: Mwenga, Kobokobo Country: Congo (RDC)
Donors Safiannikoff in year 1972

So for the occurence of As we have a primary mineral, and also scorodite in green crusts. Pb could originate from U half life and from plumbomicrolite as in dumontite and kamitugaite, but I have never seen samples of beudantite from Kobokobo. Samples of discredited lusungite (of Van Wambeke 1958) from Kobokobo have proven to be goyazite or benauite, and those crystals are very similar to beudantite.

By the way, part of the samples of "Bolivarite" of Van Wambeke (1971) from Kobokobo are probably IMA2009-057

Alain

Re: Unidentified Micros from Rhode Island

Rob Woodside — Wed, 25 Nov 2009 17:22:56 +0000

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

Re: Green rock help please

Amanda Hawkins — Wed, 25 Nov 2009 17:22:40 +0000

oh no , really lost now!

Re: Green rock help please

Rob Woodside — Wed, 25 Nov 2009 17:18:20 +0000

Don, I'm a little puzzled by your specific gravity recipe. Specific gravity is the ratio of the density of the material to the density of water, giving a pure number as your recipe suggests. However the ratio of the two weights hides the density which is crucial. With mass in grams and volumes in cm³, the density of water is 1.0 gm/cm³, so in these units the specific gravity is the numerical value of the material's density in gm/cm³. To get this density, one remembers Archimedes and the weight in water (m) is the weight in air (M) diminshed by the weight of water displaced (md), giving:

m = M - md or md = M - m

Since the density of water is 1.0 in these units, the volume of the material in cm³ is the numerical value of md in gm. This gives specific gravity as:

SG = M/md = M/( M-m)

which is not M/m

Re: Green rock help please

Amanda Hawkins — Wed, 25 Nov 2009 17:01:45 +0000

Wow Jamey, that's impressive! And thanks so much for your kind offer. I'm afraid I'm based in the UK. I think I have some smaller bits I could post to you? Would that be OK? I will sort through the box!

But I'm still thinking its nephrite myself. The black specks are the glittering bits, they don't look like the silvery glittery bits in Aventurine, which I have pieces of.

Amanda:)-D

Re: Unidentified Micros from Rhode Island

Jonathan Woolley — Wed, 25 Nov 2009 16:55:25 +0000

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.

Re: Small yellow sprays of unknown mineral from Poonah

Marco Barsanti — Wed, 25 Nov 2009 16:48:34 +0000

Thanks for the suggestions, i'll check when at home in the weekend

@ Thomas: i think with "Naski" you meant Nasik area? In that case i agree, it seems more a specimen coming out from there

Re: Unidentified Micros from Rhode Island

Jonathan Woolley — Wed, 25 Nov 2009 16:35:13 +0000

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.

Re: radioactive tourmaline (dravite?)

Jamey Swisher — Wed, 25 Nov 2009 16:26:37 +0000

Ronald John Gyllenhammer Wrote:
-------------------------------------------------------
Also, btw Schorl generally has
> a higher RI than Dravite anyway, ref.
> [www.mindat.org] ,
> Birefringence I can not find for F dominant
> Schorl.
>
> Ron

Schorl does not generally have an RI higher then Dravite. According to GT Pro, as well as all my Gemological test books and education, Schorl is reported to have an RI of 1.624-1.67 Bif. .016-.046 and Dravite is reported to have an RI of 1.604-1.675 Bif. .016-.032, giving it a .005 possible higher RI over Schorl while Schorl has the larger Bif., with the Tourmaline Group as a whole having an RI of 1.603-1.820 Bif. .016-.046. Ref= GT Pro, my class notes & materials, education & experience.

But I do agree that at this point, there seems to be no other choice, but for this material to be part of the Tourmaline group.

Re: Green rock help please

Jamey Swisher — Wed, 25 Nov 2009 16:11:24 +0000

The specks glittering could still be the Nephrite from Wyoming or other locality, but it could also open up the possibility of Aventurine as well.

The only sure fire way to figure this out now is to follow the suggestions and get a specific gravity of a piece.

Amanda, are you by any chance close to southern Pennsylvania? If so drop me an IM/PM and I can help. I would be more then willing to run full lab tests with the equipment I have at no charge for you. We have a fully featured "lab" here for the most part, aside from some of the super expensive machines(they are coming later when we save enough). Yes, we also have the education to properly use them too. ;)
•Custom Ocean Optics S2000 USB UV-VIS 200-850nm range Spectrophotometer
•SW/MW/LW UV Lighting
•400nm UV lighting
•150w Halogen Fiber Optic Lighting
•High End 3.5-95x Magnification w/ Darkfield Illumination
•Diffraction Grating Handheld Spectrometer
•Polariscope
•Dichroscope
•Refractometer
•Reflectivity Meter
•Darkfield Loupe
•Chelsea Filter
•Specific Gravity setup
•Precision balances
•Electronic metal tester
•Full photographic lab and equipment setup for close-up, macro, micro, IR, true color, and UV photography.

We have access to cheap FT-IR testing as well as some other higher end equipment.

Re: Unidentified Micros from Rhode Island

steven garza — Wed, 25 Nov 2009 15:53:23 +0000

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

Re: Green rock help please

Donald Peck — Wed, 25 Nov 2009 15:42:01 +0000

Amanda,

From your saying that the piece weighs 368g I surmise that you have got a scale of some kind. So , , , suspend the piece by a length of thread from the pan (or hook) of the scale, submerge the suspended piece in water, and weigh it again. Divide the weight in air by (the weight in air - the weight in water). That will give you the mineral's specific gravity.

Re: Mali white xl unknown

Pavel Kartashov — Wed, 25 Nov 2009 10:43:05 +0000

Similar coloured white to colourless Al- and OH-bearing members of titanite-vuagnatite series are known from garnet-eidote, garnet-vesuvianite and garnet-chlorite skarns of Southern Ural for a long time.

Malayaite is typical for more high temperature pyroxen-siderophylite-fluorite, pyroxen-axinite, garnet-pyroxen skarns where pyroxen is hedenbergite or hedenbergit-diopside and garnet is andradite.

Not all malayaites are fluorescent well - only Fe-free. But I would be very surprised, if malayaite will be found in Mali skarns.

Re: Mali white xl unknown

Timothy Greenland — Wed, 25 Nov 2009 09:18:58 +0000

If its Malayite, it should fluoresce well under SW.

Tim

Mordenite (epimorph after anhydrate} with quartz.

Greg Dainty — Wed, 25 Nov 2009 09:17:41 +0000

Can it be assumed that the specimen,from Irai, Brazil, in the attached pic, is also Mordenite (epimorph after anhydrite) on quartz. It is extremely similar to the Irai, specimen labeled so , on the mindat, mordenite page. Thanks you. ...Greg

Re: Green rock help please

Amanda Hawkins — Wed, 25 Nov 2009 08:46:13 +0000

If this helps the piece weighs 368g and the dimensions are 90mm x 56mm x 50mm roughly.

Re: Green rock help please

Amanda Hawkins — Wed, 25 Nov 2009 08:44:11 +0000

It's a hexagonal sapphire, dark blue :-)

Re: Mali white xl unknown

Knut Eldjarn — Wed, 25 Nov 2009 08:39:41 +0000

Saul,
the morphology and paragenesis fits Titanite - as stated by the others. I only wonder about you stating the occurence with "altered" Epidote suggesting some kind of additional hydrothermal event. It could still very well be Titanite - but i.e. the much rarer isostructural mineral Malayite (contaning Sn) could make similar crystals (and would be easily overlooked if ID is only based on morphology).. I know it is a "long shot" as there are no other Sn-bearing minerals listed from the area - but an EDS would simply verify the correct ID.
Knut

Re: Locality problems after Intergem Antwerp 2009

Knut Eldjarn — Wed, 25 Nov 2009 08:27:16 +0000

Vik, the no. 3 is also the strange one since the Kobokobo pegmatite is known for both primary and secondary phosphates ( including especially a number of rare secondary U-minerals) - but as far as I have been able to read no As-bearing minerals. But I know that segregations of Arsenopyrite or Löllingite may occur very locally in some pegmatites and during alteration the minerals you mention may easily be formed. Still I woud list the locality information as doubtful. It may of course be from another locality in the area.
Knut

Re: Mali white xl unknown

Saul Krotki — Wed, 25 Nov 2009 05:20:42 +0000

Thanks, Pavel, Uwe, and Stuart, for your immediate response. I was not familiar with white titanite but later found examples from Piedmont, Italy in the mindat galleries that were a good match. I updated the mindat Koukouri, Kayes Regiond, Mali mineral list and added the titanite.

These are very sharp crystals and great for photomicrographs. I didn't know that I had purchase them, having only admired the grossular and epidote combinations when I obtained the specimens. Something worth watching out for.

Enjoy!

[www.mindat.org]

Re: Unidentified Micros from Rhode Island

Michael Kieron — Wed, 25 Nov 2009 05:17:43 +0000

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.

Re: Metalic Mine maybe Zinc

Ronald John Gyllenhammer — Wed, 25 Nov 2009 02:15:01 +0000

Hi Tayfun,

Value is in the eye of the beholder. You now have a specimen you've collected and identified, there is your value. Goethite is a member of the Diaspore Group. Goethite is common, if you want monetary value look for Diaspore. [www.mindat.org] In the mean time, enjoy that which you've collected. All the best. :)

Ron

Mindat Mineralogy Messageboard - Identity Help

Re: radioactive tourmaline (dravite?)

Re: Green rock help please

Re: Green rock help please

Re: Unidentified Micros from Rhode Island

Re: radioactive tourmaline (dravite?)

Re: Small yellow sprays of unknown mineral from Poonah

Re: Green rock help please

Re: Green rock help please

Re: Locality problems after Intergem Antwerp 2009

Re: Unidentified Micros from Rhode Island

Re: Green rock help please

Re: Green rock help please

Re: Green rock help please

Re: Unidentified Micros from Rhode Island

Re: Small yellow sprays of unknown mineral from Poonah

Re: Unidentified Micros from Rhode Island

Re: radioactive tourmaline (dravite?)

Re: Green rock help please

Re: Unidentified Micros from Rhode Island

Re: Green rock help please

Re: Mali white xl unknown

Re: Mali white xl unknown

Mordenite (epimorph after anhydrate} with quartz.

Re: Green rock help please

Re: Green rock help please

Re: Mali white xl unknown

Re: Locality problems after Intergem Antwerp 2009

Re: Mali white xl unknown

Re: Unidentified Micros from Rhode Island

Re: Metalic Mine maybe Zinc