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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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Posted: Sep 15, 2011 22:28 Post subject: Re: Mineral specimens with inclusions |
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xenolithos wrote: | Sometimes cutting is necessary to reveal the inner beauty of battered crystals and I only cut damaged specimens. Here is an example cut from a broken Madagascan quartz point, keeping the original outline to show up the hollandite (or so I am told) sprays decorating a phantom face, now near the bottom of the stone. Hope you enjoy it! |
I have been enjoying it and have shown it to several people, along with this great thread. I would love to have one of those in my collection! From your description, I imagine that the phantom followed the rhombohedral faces and so from the side, the spiders might appear to be rising up, with the center leading the flock - as if the c-axis was drawing it along? or more like urchins churned up in the sea - not to mix metaphors too much, but inclusion scenes do lend themselves to runaway imaginations.
xenolithos wrote: | We all need a Raman spectroscope in the garage! |
No Raman in my garage yet, though a friend wants me to build one together (easy he says - he built the one seen in the image below). An early description of the hollandite inclusions appears in G&G Fall 2001, p. 238 - they were confirmed by breaking them out of the quartz and using X-ray diffraction; there is a neat SEM image as well...what I find more to the point is that "the shape of the needles is consistent with monoclinic pseudotetragonal crystal habit of hollandite". Part of what I am learning to do, with the patient help of a mineralogist, is to learn more about crystallography and be able to recognize these attributes in the mineral inclusions I find, as well as to relate them to the host mineral (along with the interaction between the two during growth). So far, that hasn't helped in figuring out the ones shown in the spinel below. At the time I took the photo, I did not know to look at the cross-section of the inclusion as it breaks the surface - one of the first things I look for now.
Best wishes,
Elise
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Unknown inclusions in cobalt spinel (photo: E. Skalwold) |
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Raman set-up, covers removed. |
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_________________ Elise Skalwold |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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Posted: Sep 16, 2011 16:59 Post subject: Re: Mineral specimens with inclusions |
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Elise wrote: | Part of what I am learning to do, with the patient help of a mineralogist, is to learn more about crystallography and be able to recognize these attributes in the mineral inclusions I find, as well as to relate them to the host mineral (along with the interaction between the two during growth). |
I am replying to my own posts (yikes) - I would like to give a better example for that comment. The quartz specimen below has beautiful sprays of ankangite needles identified by a mineralogist (these were first described as a quartz inclusion in G&G Sp. 2009). The large inclusion amid the needles appears to me to be monoclinic; it is translucent white and is similar to orthoclase (the crystal has shrunk so there is some reflection from the interface). The ankangite is a tetragonal barium rich oxide mineral; the other inclusion is likely celsian, another barium rich mineral and known to be associated with ankangite. The photo in the G&G does not show the celsian very well, nor does it describe it other than saying it is euhedral and white or colorless. The optical orientation of the fashioned cabochon is with the optic axis - which is also the c axis in quartz - perpendicular to the top and displaying an Airy's spiral optic figure with a conoscope and crossed polars. Regrettably, though the inclusion is large, it is not transparent enough to determine its optical nature. So, for now maybe the other clues give enough confidence. This is my rarest mineral in my collection and the rarest association as well....and small enough that I can afford to collect it at all!
Cheers!
Elise
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Ankangite needles and likely Celsian inclusions in quartz host. The celsian is actually translucent and is approx.1.75 mm (photo: E. Skalwold). |
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Ankangite needles in quartz; the large celsian inclusion at top right corner (as seen between crossed polars). Origin: Brazil. Approx. 20x13x4mm (photo: E. Skalwold). |
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Duncan Miller
Joined: 25 Apr 2009
Posts: 138
Location: South Africa
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Posted: Sep 17, 2011 01:58 Post subject: Re: Mineral specimens with inclusions |
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Elise wrote: | From your description, I imagine that the phantom followed the rhombohedral faces and so from the side, the spiders might appear to be rising up, with the center leading the flock - as if the c-axis was drawing it along?Elise |
Elise - First, thanks for you confirmation that the spiders are hollandite. Yes, they are on the phantom's rhombohedral faces, with the optic axis running vertically through the stone. There is no table, only six shallow crown facets meeting at a point. The hollandite sprays are just inside the pavilion facets. It is very satisfying to play with crystallography in this way, and recover something pretty from what was a sadly damaged crystal termination.
Duncan
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Antonio Alcaide
Site Admin
Joined: 23 Aug 2009
Posts: 314
Location: Spain
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Posted: Sep 18, 2011 04:37 Post subject: Re: Mineral specimens with inclusions |
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xenolithos wrote: | It is very satisfying to play with crystallography in this way, and recover something pretty from what was a sadly damaged crystal termination. |
Really, Duncan, most of the hollandite included quartz I have seen were damaged but, thank to this great thread and all your contributions, I am learning that also in mineralogy -as in other fields of life- the interior could be better than the exterior.
Elise wrote: | there is a neat SEM image as well... |
Altough I know in this case you mention a SEM image of an article, please post them -SEM images- when possible. I have just started a collection of SEM pictures. They are the definitive way to approach to the crystallography and inner structure of minerals, no matter the B&W.
Best regards
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Duncan Miller
Joined: 25 Apr 2009
Posts: 138
Location: South Africa
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Posted: Sep 19, 2011 08:23 Post subject: Re: Mineral specimens with inclusions |
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Debbie Woolf's beautiful Namibian quartz with haematite inclusions is a very characteristic specimen, with the inclusions concentrated towards the termination. Looking at her photographs and my own, not so wonderful, specimen it appears the inclusion platelets are not entirely randomly distributed. They don't seem to lie on phantom rhombohedral faces, but appear to be more or less, also not precisely, perpendicular to the rhombohedral faces. This is a similar orientation to the wispy 'tadpole' inclusions of haematite in much of the so-called Orange/Gariep river quartz, which cross the purple/colourless phantom banding. I am going to break my own undertaking not to post any more cut stones here, and post two showing this. The one shows an amethyst phantom with two lateral 'bug eyes', which consist of remnants of the original haematite coating of two of the rhombohedral crystal faces, very cleverly retained by the cutter, as in Elise's opening example. The other is a crudely back-lit amethyst cabochon, in which the haematite 'tadpoles' clearly cut across the purple banding (here looking curved because of the lensing effect of the cabochon). Both are difficult to photograph, so please excuse the quality of the images. The point is that there appears to be *some* crystallographic control of the haematite inclusion growth, but not a strict one.
Duncan
PS For those who don't know, the Orange river between South Africa and Namibia is now known locally as the Gariep. I don't think you need to rush to change your labels, but knowing it might avoid some confusion.
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Quartz, amethyst phantom, haematite inclusions and coating Orange/Gariep river, probably southern Namibia about 30 mm long |
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Quartz, amethyst, hematite inclusions Orange/Gariep river, South Africa 35 mm long |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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Posted: Sep 19, 2011 11:19 Post subject: Re: Mineral specimens with inclusions |
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xenolithos wrote: | I am going to break my own undertaking not to post any more cut stones here... |
Remember one premise from the beginning of this thread: inclusions are just fine mineral specimens with expertly trimmed matrix....
The color zoning in the above amethyst almost looks reminiscent of a trapiche pattern in the way the darker colors outline the sectors.
Below, a side-view image showing a spray of an acicular Cu-bearing blue mineral with pseudomorphs of native copper taking over. My specimen is very murky, which doesn't make for good photos, but I hope shows how special these inclusions are. They nucleate in a plane just above a colorless area in the host quartz (it looks black in the photo because of the lighting). This one shows both minerals, but elsewhere the tufts are all blue or all copper; the latter strongly resemble goethite tufts to the naked eye. These are from the Paraiba state of Brazil; I won't mention by what name the material is marketed as.
Elise
Description: |
Quartz containing inclusions of blue Cu-bearing acicular mineral sprays with pseudomorphs of native copper, approx. 1.5mm, Paraiba, Brazil (photo: E. Skalwold). |
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Duncan Miller
Joined: 25 Apr 2009
Posts: 138
Location: South Africa
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Posted: Sep 19, 2011 12:55 Post subject: Re: Mineral specimens with inclusions |
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Elise - How do you know the copper is replacing the blue mineral, and not the other way around?
Debbie - Here are my two Goboboseb crystals (cropped, not chopped!), showing the orientated haematite inclusions.
Duncan
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Quartz, haematite Goboboseb, Namibia 20 mm wide |
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Quartz, haematite Goboboseb, Namibia 13 mm wide |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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Posted: Sep 20, 2011 12:16 Post subject: Re: Mineral specimens with inclusions |
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xenolithos wrote: | Elise - How do you know the copper is replacing the blue mineral, and not the other way around? |
Hi - This specimen is part of a study collection where the inclusions have been identified already for me by a mineralogist specializing in inclusions; I work "backwards" to try to understand how and why. The blue fibrous inclusions are presumably a copper-bearing silicate such as shattuckite or papogoite (others plancheite, kinoite and ajoite) -- that specimen is from Brazil; I am not sure what is known about the blue sprays from there other than that they are found as phantom layers in the same specimens as gilalite inclusions are found (some gilalite resemble blue jellyfish medusae); both types referred to as Paraiba quartz by some.
Maybe someone has an intact crystal which shows either or both together. This is the only example I have seen where the blue fibers have been taken over by the copper; the entire specimen is reddish with only a small area of blue fibers left. So, together with what was told to me by the mineralogist, I am assuming that the blue is what remains of a phantom layer of blue tufts; the rest is a native copper pseudomorph after an unidentified blue copper silicate.
Does copper crystallize in a fibrous form? If the form is unusual for a mineral, isn't that one indication of a pseudomorph? I am thinking back to when I first heard that term which was from Jeff Scovil while watching him image an opal "pineapple" (2003?) which later appeared in the Lithographie Opal issue. I had never seen such an amazing opal (and didn't know at the time that I was also seeing an amazing example) and the whole idea of the process was an intriguing concept ( is there a pseudmorph thread on FMF?). Applying that to how it might happen in the case of an inclusion is a bit of a mystery to me. Did the blue phantom layer get replaced by copper before the new quartz growth enveloped it? or during younger quartz crystallization or even afterwards? How much migration and replacement takes place during those different phases? It's the stuff that makes talk around the campfire go into the wee hours.
Cheers!
Elise
PS: I have to backtrack to the ankangite & celsian photo above - I assumed that the metallic look of the celsian was due to it shrinking more than the quartz, creating a void around the crystal. But, today I got a mini-lesson in thermal expansivity from an expert and realize this might not be the case for that metallic look of the celsian. The quartz shrinks more than the feldspar so there probably isn't a void; maybe a difference in refractive index or a surface deposition causes the effect. Anyway, I had wrongly applied what I knew about a chromium pyrope garnet inclusion in diamond to a different set of minerals (the garnet shrinks more than the diamond host and a void was created causing a similar effect in a specimen I was trying to image).
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Scott LaBorde
Joined: 14 Dec 2009
Posts: 104
Location: North Carolina
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Posted: Oct 05, 2011 07:41 Post subject: Re: Mineral specimens with inclusions |
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This is quartz with specular hematite phantoms I found while digging in Chatham County, NC. Although my rockhound buddies and I recovered over a thousand crystals from this location, there were only a few that had phantoms that were so distinct and thick with the sparkling hematite.
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am mizunaka
Joined: 09 Apr 2010
Posts: 2053
Location: USA
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Posted: Nov 29, 2011 06:08 Post subject: Re: Mineral specimens with inclusions |
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Quartz with Anatase Polar Urals, Western-Siberian Region, Russia 10.2 x 7.2 cm. |
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cascaillou
Joined: 27 Nov 2011
Posts: 250
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Posted: Nov 30, 2011 13:47 Post subject: Re: Mineral specimens with inclusions |
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I'm fascinated with inclusions, however it is really a shame that such crystals very frequently have their facets polished. I'm struggling to get my hands on unpolished included crystals. Not only polished crystals are usually ugly, but also polishing erases their cristallographic characteristics (erased growth features, softened edges, convex facets).
I can understand that a crystal might be polished when its surface is so opaque that interesting inclusions cannot be seen correctly , even with immersion. But unfortunately it seems that polishing is done in a routine, no matter what the transparency of the crystal is, which is a pity.
By the way, let's talk about immersion technique:
The outlines of a transluscent to transparent stone will disappear when the stone is immersed in a liquid that has the same refractive index than the stone (or they will fade in a liquid of close RI). However, inclusions will remain perfectly visible, which makes immersion very useful for examination of the inclusions under the microscope. Also, if a stone has a very disrupted or scratched surface, that might be the only way to comfortably examine its inclusions.
Here's a list of immersion liquids, by increasing RI value:
water= RI is 1.33
ethyl alcohol= 1.36 (non toxic, weak smell, colorless, flammable)
sunflower oil: about 1.47 (non toxic, odourless, yellowish)
glycerin= 1.473 (non toxic, odourless, colorless, for sale at the pharmacy)
toluene= 1.494 (toxic, smelly, flammable, for sale at the hardware shop)
sandalwood oil= 1.50 to 1.51 (yellowish)
anise oil= 1.54 to 1.56 (yellowish)
Refractol= 1.567 (non toxic, odourless, colorless, oily liquid, for sale online)
benzyl benzoate= 1.57 (a bit toxic, smelly, colorless, oily liquid)
cinnamon oil= 1.59 to 1.60 (yellowish)
Trugem immersion liquid= 1.62 (non toxic, colorless, for sale online)
monobromonaphtalene= 1.66 (toxic vapours with bad smell)
1-Iodonaphthalene= 1.70 (toxic vapours with bad smell)
diiodomethane (aka methylene iodide)= 1.74 (toxic vapours with bad smell)
Nothing too toxic in this list, chemicals I described as toxic would rather be labelled 'harmful' actually, but care must still be taken with the latest three.
Let's also note that I mentionned a few natural oils but these are normally not used for immersion purposes, I mentionned these only for reference.
Also this website is selling immersion liquids of many different RI (1.30 to 1.70):
www(dot)cargille(dot)com(slash)immerliq(dot)shtml
About diiodomethane:
Notably, it is very useful for immersion of corundum, but it's quite an expensive chemical, and note that some chemical supplier won't sell to private individuals.
Best price I could find was a US supplier: 87$ for 500g (that is 150mL) for 98.5% purity diiodomethane stabilized with copper
Second best price was a european supplier: 250$ for 1Kg (that is 300mL) for 99% purity diiodomethane stabilized with copper.
Be careful as some suppliers ask completely excessive prices such as 500$ for 1kg !
To lengthen shelf life of diiodomethane, it's best to place in the vial a tiny piece of copper shaving (or even better copper foil), also diidomethane must be stored away from light and heat, in a tightly closed airtight vial.
The immersion cell:
The easy way to go is to use any small glass container (not plastic!), colorless and perfectly transparent, which will work just fine for a vertical microscope (for instance a tiny jam glass jar). However, if you want to examinate stones in polarized light, you would want the glass to be strain-free (which you can check between crossed polars)
For horizontal microscopes, you would need to buy a cube-shaped immersion cell made of strain-free optical glass, but these cost around 100$. You can get one from mikon-online(dot)com
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Tracy
Joined: 15 Sep 2006
Posts: 551
Location: Toronto
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Posted: Nov 30, 2011 14:28 Post subject: Re: Mineral specimens with inclusions |
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Hi Cascaillou -
There is no "harmful" label in the US, so your reference to it is meaningless over here. In fact there is (as yet) no universally adopted system for classifying materials as to their toxicity. Terms like "toxic," "a bit toxic" and "nontoxic" will not tell you anything without supporting health hazard information. For all of the chemicals you list, I would recommend checking with the chemical supply company and/or a toxicology resource to get an understanding of each substance's hazard potential, and refer to a Safety Data Sheet and/or industrial hygiene resource for safe handling recommendations.
("All substances are poisons, and nothing is without poison; only the dose permits something not to be poisonous" -Paracelcus)
With apologies for the non-mineralogical digression
- Tracy
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cascaillou
Joined: 27 Nov 2011
Posts: 250
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Posted: Nov 30, 2011 15:00 Post subject: Re: Mineral specimens with inclusions |
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I have of course checked the MSDS of each of these chemicals, it should be ok as long as you work in a well ventilated room.
Let's note that Refractol and Trugem liquids are non-toxic. I bought some refractol (cheap) for immersion of quartz.
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Tracy
Joined: 15 Sep 2006
Posts: 551
Location: Toronto
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Posted: Nov 30, 2011 15:59 Post subject: Re: Mineral specimens with inclusions |
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I didn't mean to be critical Cascaillou, and can see how it might have come across that way. I just wanted to advise Forum readers that hazard is relative (toxic/nontoxic) and needs to be looked upon with an informed mind. Apologies if I came across as grouchy.
- Tracy
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cascaillou
Joined: 27 Nov 2011
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Posted: Nov 30, 2011 16:20 Post subject: Re: Mineral specimens with inclusions |
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No worry, I didn't take it as a criticism.
You were indeed quite right to point this out, so I just wanted to confirm that the toxicity level was fine within exposure ranges associated with common immersion use, but you might still get headache from the smelly ones if the room is insuficiently ventilated, considering that when working with a vertical microscope, you head is just above the immersion cell.
The solution is to place a plate of strain-free optical glass on top of the glass container to limit vapour emanations (actually, the cube-shaped immersion cell I mentionned does include a glass cap for that purpose).
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Matteo_Chinellato
Joined: 12 Dec 2011
Posts: 115
Location: Venice, Italy
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Posted: Dec 22, 2011 09:30 Post subject: Re: Mineral specimens with inclusions |
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Here just a Beryl from Elba Island with Columbite-(Mn) start from into the crystal and escape outside
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Beryl, Columbite-(Mn) Masso Foresi, Fonte del Prete, San Piero in Campo, Campo nell'Elba, Elba Island, Livorno Province, Tuscany, Italy 1.1 mm Beryl termination with brown-red Columbite-(Mn) crystals. Collection Adriano Perugini |
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Matteo_Chinellato
Joined: 12 Dec 2011
Posts: 115
Location: Venice, Italy
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Posted: Dec 22, 2011 09:33 Post subject: Re: Mineral specimens with inclusions |
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Here another Elba Beryl with not know inclusions
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Beryl Grotta d'Oggi Quarry, San Piero in Campo, Campo nell'Elba, Elba Island, Livorno Province, Tuscany, Italy 2.74 mm transparent Beryl crystal
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Matteo_Chinellato
Joined: 12 Dec 2011
Posts: 115
Location: Venice, Italy
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Posted: Dec 22, 2011 09:36 Post subject: Re: Mineral specimens with inclusions |
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Another Elba Beryl full of Columbite-(Mn) inclusions
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Beryl, Columbite-(Mn) Pastori Vein (Filone dei Pastori), Fosso Marcianella Pegmatite, Catri, Sant'Ilario in Campo, Campo nell'Elba, Elba Island, Livorno Province, Tuscany, Italy 1.3 cm. Beryl transparent crystal with several Columbite-(Mn) acycular crystals into |
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Matteo_Chinellato
Joined: 12 Dec 2011
Posts: 115
Location: Venice, Italy
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Posted: Dec 22, 2011 09:38 Post subject: Re: Mineral specimens with inclusions |
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Here a very nice Fluorite crystal with not know inclusion
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Fluorite Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany Transparent 1.35 mm Fluorite crystal with inclusions. Collection D.Preite |
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Matteo_Chinellato
Joined: 12 Dec 2011
Posts: 115
Location: Venice, Italy
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Posted: Dec 22, 2011 09:41 Post subject: Re: Mineral specimens with inclusions |
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A classic Quartz with dendrites
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Quartz, Manganese Oxides Galiléia, Doce valley, Minas Gerais, Brazil cutted Quartz of 3.6x2.4x1.5 cm ( 69.2 ct. ) with Dendrites inclusions. Collection & Photo M.Chinellato
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