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Tracy's favorite specimens
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Tracy




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PostPosted: Apr 15, 2008 20:42    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

New photos!

I realized as I was cataloguing some specimens over the weekend (I am almost up to 2007; note to self: get everything catalogued FASTER!) that I overlooked one of my favorite specimens acquired from Jordi, shown in photo #1. It's well-developed, scalenohedral manganoan calcite crystals of a wonderful, soft pink color, nicely draped over well formed, translucent quartz crystals. From Pachapaqui, Bolognesi, Departamento Ancash Peru, 10 cm x 8 cm x 7 cm. The quartz isn't visible from the photo, but the whole specimen is very beautiful and three-dimensional. The calcite crystals are extremely fluorescent too! To me there's a great deal to admire with this specimen.

My topic is titled "an amateur's adventures" because I want to share my own personal evolution as a collector. I've recently come to realize that I really like quartz specimens of all kinds (and there are so many different kinds!). To that end, most of the pictures I post tonight will be quartz specimens that I like.

Photo #2 is a faden quartz which I found on eBay. I like fadens; scientifically they're very interesting. Multiple breakages and re-healing with incorporation of liquid and gaseous inclusions in the areas of regrowth, all while the crystals continue to expand outward. The breakage/regrowth zone ends up looking like a white "thread-like" line within the crystal(s). Anyway, this faden is from Waziristan, Pakistan, 5 cm x 4 cm x 0.75 cm. It's a stack of tabular crystals and the faden is clearly visible throughout. The edges are nice and clear. The top crystals are thicker than the bottom ones and I'm guessing this is the reason why the whole piece is curled over a bit (not sure whether you can see this in the photo, but it's like the crystals are "leaning forward" - I tried to find an angle to show the curve that didn't create too much glare from the crystals, without complete success) - or is there another reason why the crystals aren't straight? I have seen a lot of fadens and find this one very sculptural.

NOTE: I tell what I know and am sure I don't get everything right. Please feel free to correct me, I like to learn.

Photo #3: continuing with the quartz theme, here is a specimen of light lavender chalcedony covering danburite crystal sprays, all on a sphalerite matrix. From Charcas, San Luis Potosi, Mexico, about 8 cm x 5 cm x 5 cm, ex. Martin Zinn collection. The descrption says that chalcedony over danburite over sphalerite is an interesting paragenesis, but I'm not sure what makes it interesting. Can anybody offer input? I really like this piece because it's esthetic and unusual. I also like danburite crystals (which aren't visible at all in this piece) - I read somewhere that when one gets tired of quartz crystals, a logical "next step" is danburite, because at a quick glance the danburite crystals look like quartz, but on closer examination do not have the same crystal habit (someday I'll master the terminology to express this better). Last but not least, I like chalcedony - overall a nice addition to my collection.

Hmmm, I just learned from mindat that much chalcedony isn't pure quartz, but a mixture of quartz and moganite - interesting!

Three more photos to come...



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PostPosted: Apr 15, 2008 21:11    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

New photos - part 2!

I can't add new pictures without inserting something strange and unusual. Tonight I'm posting two images of a rather peculiar ("how on earth...?") quartz specimen. From Taquaral, Itinga, Minas Gerais, Brazil, 11 cm x 6.5 cm x 5.5 cm, ex. E. Schlicter collection. It's partly white quartz, which is nicely crystallized. The other part is rose quartz, though I'd hardly call it "rose" - there is a bit of the typical pink but most of this quartz is salmon-colored. And it looks scaly, as though there were crystals which formed and subsequently melted into thick, curly blobs. The contacted part looks like a a core of deep pink or amethyst quartz. There are some mica books inserted, and a couple of yellow-ish crystals which might be nothing more than discolored quartz - I do not know what they are. I'm attaching 2 photos, one of each side, to show you as much as I can. Not an esthetic piece, but a mysterious specimen to me! How was it made? - explanations would be greatly appreciated.

Finally: just to prove that my collection isn't 100% quartz, fluorite and other "beginner" minerals, here's a nice aquamarine surrounded by columns of muscovite crystals and albite. From Shigar Valley, Gilgit, Northern Pakistan, 8.5 cm x 6,5 cm x 5.5 cm. The aquamarine has richer color than is shown in the photo. There is nothing unusual about this combination of minerals from Pakistan, but it's a pretty specimen I'm proud to share.

I wanted to write a bit about a wonderful book about minerals that I'm reading - another chapter of my adventure - but out of time tonight. Maybe tomorrow...



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PostPosted: Apr 18, 2008 09:08    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Tracy, I love your "woman" taste in minerals as well as your fine blend of scientific facts. I get the sense that you are truly attached to your pieces and you are constantly developing an unusual collection? Can we see more???
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PostPosted: Apr 18, 2008 09:34    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Absolutely!. When you will publish more Tracy?

BTW, I already corrected in your text "Tacquerel" location. The correct name should be: Taquaral, Itinga, Minas Gerais, BRAZIL.

Jordi
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PostPosted: Apr 18, 2008 21:00    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Thanks for the kind words! And thanks for the correction Jordi, I've revised my label with your information.

Once a scientist, always a scientist...there is just so much I enjoy learning. The mineral universe is great because there are so many things to investigate.

Not many photos to publish tonight but I will take more after the weekend. In the meantime I would like to share one of my recent personal adventures:

Last month I was browsing in an old book store and came across a book titled "Getting Acquainted with Minerals," by George Letchworth English, published in 1934. It wasn't very long and it seemed easy enough to read, so I bought it figuring it would be fun train reading. What a great book this has turned out to be! The author describes it as a text suitable for all ages, and it's a great beginner text. Best of all are the chapters devoted to crystal systems. He walks you through all the different systems using potatoes as a teaching aid - yes, potatoes! He has the reader start with a 2-inch cube and shows how to create different crystals by trimming away edges and corners. Extremely easy to visualize, even though I wasn't cutiing potatoes on my train ride. :-) Also would make a fun exercise for kids. Anyway, my knowledge of crystallography has always been weak but in reading this book I'm happy to say that a lot of pieces came together for me, and I can talk about crystals with a much greater sense of confidence now. Hooray!

(John: OK, now I can see how quartz hexagons are made from two rhombohedrons joined together. What I'm not clear on is why and how two, and only two, distinct crystals would fuse this way to form separate crystals.)

The book doesn't teach much else in depth, and only touches briefly on other topics like twinning and pseudomorphs, but it's great fun as a starter (apparently in 1934 you could get a complete set of "hardness scale" crystals for 70 cents - how things have changed!). And there are 11 copies available from Amazon in case anyone is interested in geting their own copy.

Prof. English recommends starting out with a set of small specimens that one would be willing to pound on, stretch, bend, scratch, and in general treat very badly, then slowly moving on to better specimens that will be a part of one's permanent collection. If that truly is the way to learn about minerals, then I have been doing things very out of order...

So that's the story. I don't want to ramble for too long because I've already noticed that a lot of my questions go unanswered and maybe it's because I write too much that they get lost. So here are my outstanding questions from the last set I published:
1) am I correct that my faden leans forward because the top crystal is wider than the others? (Bob G if you are reading this, thanks for your note - glad you like the faden) I can take a picture of it from the side if it would help.

2) Can anyone tell me why my strange rose quartz specimen is salmon-colored instead of pink, and why the crystals are so deformed even though the white crystals right next to them are sharply defined?

And, from an earlier posting: any more ideas on how my "egg" specimen was formed? Will it help if I photograph it from different angles?

My pictures for the evening: first is a rose quartz crystal cluster attached to a book of "angel-wing" mica, on feldspar. From Pitorra Mine, Galileia, Minas Gerais, Brazil, 5.5 cm x 3.5 cm x 3.5 cm. I don't have a good stand to display it and it deserves to be seen from more than one angle, but this was the best of my photos. Nice color and good esthetics. The crystals aren't that easy to see from the picture but they are sharp and well formed.


Photo #2 is a dioptase specimen I got from Jordi. From Tantara Mine, 20m↓, Kakounde, Likasi, Shaba Congo D.R., 3.8 cm × 3.1 cm × 2.2 cm. Excellent esthetics, good crystals, rich green color, and much better than my old dioptase specimen. Not something I would normally be interested in but I took a chance, and it stands out beautifully from among my other specimens.

No other photos to share, will start on a new set after the weekend.



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PostPosted: Apr 18, 2008 22:43    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Hi Tracy,

Again, another nice set of photos. I wish I could find the time to photograph some of my pieces. Maybe someday soon.

As to the faden, and maybe Les can chime in as he has some experience with those from Arizona, they are formed in a cataclastic environment. What I have seen in matrix specimens from the Quartzsite area of Arizona, is that the "thread" is attached on each side to the sides of a crack in the matrix. I presume that as the rock was deformed a small quartz crystal was "stretched out" across the crack. Because the stress field is not uniform on a small scale, these "threads" may not be linear, and thus often have bends or other distortions.

The "thread" acts as a nucleation center for subsequent quartz crystallization, and the resulting crystals tend to follow the "thread"'s distortions. That is why your specimen is not uniform.

An interesting question, that I really haven't thought much about, is why the resulting fadens tend to be flattened or tabular in habit. And, why they are often symmetrically centered on the "thread". Neither of these properties are universal as I have examples that violate both of these generalizations, but nonetheless, most fadens do fit these properties. I suspect these crystals are formed at fairly low temperatures, but need to do more research.

Does this answer question 1?

Bob

BTW, there is a fairly recent book out on Quartz called "Quartz" by Harold Dibble. I think Nevada Mineral and Books (google it) carries it.
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PostPosted: Apr 19, 2008 12:09    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Thanks Bob, you've answered question 1. But now I'm curious to know the answers to the questions you've added: 1a) why are faden crystals usually tabular and 1b) why are they often centered symmetrically around the thread? (we can start a new topic on fadens if need be)

I hastily snapped a couple of photos this morning. Two are of my faden, one is a side view and the other a better view of the front. The crystals bend and (I never noticed this before) twist a bit too. For orientation, the bend is toward the camera if you are looking at it frontwise.

Thanks too for recommending the quartz book, I will look for it.

And a third photo, just for fun, of a sand calcite from Rattlesnake Buttes, South Dakota. 10 cm x 9.5 cm x 7 cm, ex. S. Chamberlain collection. Sculptural and soothing in color.

Gotta run, more photos next week. I just got some new quartz specimens, am very excited! And if my curious kitten lets me, will rummage through my boxes for other fun things to share (open cupboards are an invitation to explore and knock everything over).

Happy Saturday!



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PostPosted: Apr 27, 2008 22:13    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Had a few minutes tonight, so I thought I'd post a few more photos.

Gail's fluorapatite "The Tree" was so superb and sculptural. I have nothing similar to it, but it did make me thing of stalactites (which I like very much) so that is the theme of this set.

First is a pair of quartz stalactites from Jalgoan, Maharashtra, India. About 9 x 4.5 x 2.5 cm (excluding the matrix rock at the base). I like the way these stalactites curl toward each other, it reminds me of a Henry Moore sculpture. I find this pair to be very esthetic.

Second is a pyrite stalactite from Da Ching mine, Da Ching, Guangxi Province, China. ex. Marty Zinn collection. It is roughly 11 x 1 x 0.75 cm. The pyrite crystals formed as very small plates that look like the scales of a snake. It is not very apparent from the photo, but there are some areas of iridescence too. This stalactite deserves to be displayed vertically but unfortunately I don't have the right kind of stand. I really like its shape and texture.

Finally I am posting a photo of a pyromorphite stalactite from Les Farges, Ussel, Correza, Limousin, France. ex. Gerald Clark collection. About 5.5 x 2.5 x 2 cm. the well-formed barrel-shaped crystals are caramel colored (they look washed-out in places, but that's the camera flash) except at the tips, where they are yellow-green. To my knowledge pyromorphote stalactites aren't all that common, though I could be wrong. If only it was the classic Les Farges green color...oh well, I'll keep it anyway! :-)

Time for sleep now.



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PostPosted: Jul 01, 2008 21:56    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

The Forum is back online! And I haven't posted any photos in a while. I have a rare few minutes tonight to publish some...unfortunately I only have a handful because the others didn't come out good at all. Back by popular demand...?

First is an esthetic specimen of skeletal white calcite rhombs, arranged in a V-shaped formation. It reminds me of a flock of flying birds. I tried, but the photo doesn't show the 3-dimensionality as well as I would have liked; it has more depth than I was able to capture and the white color of the crystals makes them look a bit blurry, even though the image is in focus. From Wenshan, Yunnan Province, China. 11 x 6 x 5 cm

The next photos are of some interesting Bolivian pyromorphites I recently obtained. I think they are interesting because the crystals are sharp and, from what I understand, green pyromorphites from Bolivia aren't very common. There are 2 specimens, each with different crystal habits (with close-ups of the crystals). The first specimen is 5.5 x 3.5 x 2 cm with hexagonal crystals, and the second is 4.2 x 2.5 x 2 cm with "wheat sheaf-like" crystals. From Huari-Huari Mine, Potosi Department, Bolivia. (thanks to Brian Kosnar for the photos).

Finally, my favorite of this group is a quartz specimen which I recently obtained. It is a double-terminated crystal which "cradles" 4 smaller points in the middle. One of the smaller quartzes wraps across 3 faces of the large crystal. The smaller crystals probably grew from seed crystals which appeared on the surface of the larger crystal as it was still growing. The crystals have cloudy centers but the outer few millimeters are very clear. Except for one small ding at the left-side tip of the large crystal, the points are all undamaged. Also, there is a small area that is either damaged or evidence of a contact point so I think it is a floater, but maybe not. I had a chance to photograph this when the sunlight was just right and I like the way the picture ended up. From Honghe, Yunnan Province, China, 10.5 x 5 x 5 cm. NOTE: John and Les have both seen this specimen up close, and I invite them to add any comments they might have about it.

Work is extremely busy right now but I have other favorites yet to post! :-) I also promised to write a summary of my visit to the Smithsonian - as soon as I can. In brief, it was amazing.

- Tracy



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PostPosted: Jul 01, 2008 22:07    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Hi Tracy,
Nice to hear from you again. This set is really neat. I particularly like the calcite specimen and the quartz, as I am fond of these species. Look forward to more of your posts.
Bob
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PostPosted: Jul 01, 2008 22:15    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Tracy, good to hear from you! I can't wait to hear your Smithsonian Mineral stories.
What fabulous photos of your specimens, I see you can add a lot to each posting too.
Hope you are keeping well and glad to see you are posting again. Good work!

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PostPosted: Dec 12, 2008 13:42    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Tracy, you still alive girl???? Can we see more of your minerals please???
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PostPosted: Dec 12, 2008 14:46    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Hi Gail -

Still alive but drowning in more work than one human being can handle. Will try to get some new photos up soon, I have other cool specimens to share.

Happy weekend!
Tracy

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PostPosted: Dec 14, 2008 20:41    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

One specimen to share tonight: a recently acquired schorl crystal with lots of needle-like projections at one end. It reminds me of a black come. The cool thing is that, though it looks black under regular lighting, under a bright light (in the case of the photo below, the flash from my camera), the needles are purple. I confess I know very little about tourmalines and how they form, and I don't know whether this a second growth stage of elbaite-like "needle" crystals, or whether the entire crystal is schorl-elbaite? Alternatively, were the needles formed by etching processes? Regardless I think it's neat, but if anyone can help me understand how it came to be I'd be grateful...photos below

From Corcunda Mine, Governador Valdares, Brazil. 8 x 2.5 x 2 cm. Ex. Robert C. Lambert collection.

Lining up another batch that I will post when when time permits.

- Tracy



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PostPosted: Dec 15, 2008 05:47    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

I can't be sure, but for me the specimen comes from Golconda mine (Governador Valadares, Minas Gerais) or from Serra Corcunda area (Alagoas, Brazil) but not from Corcunda Mine, that, as far as I know, it don't exist.

Nice specimen!

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PostPosted: Dec 15, 2008 08:44    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

A very interesting schorl crystal. The hairs are due to accelerated crystal growth along one axis. I know that John White or Peter Modreski can explain it much more eloquently and scientifically but envision a cubic cuprite crystal that is able to form a long needle-like crystal in the chalcotrichite form. We see wulfenite crystals due the same thing as your schorl. As far as I know, it is all schorl.
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PostPosted: Dec 15, 2008 08:58    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

I have one of these I acquired from Frank and Wendy Melancon. We call it the "Don King" tourmaline after the boxing promoter with the hairdo. Mine is labeled Corcunda Mine, Gouvenador Valadares, MG, Brazil.
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PostPosted: Dec 15, 2008 09:10    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Some of these "haired" terminations on Minas Gerais Schorl are Foitite.
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Tracy




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PostPosted: Dec 15, 2008 09:48    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Carles - Making sure I understand correctly, might this be foitite growing on schorl? According to mindat, there are no localities for foitite in South America., but the description and the photos are consistent with foitite.

Mary - I still encision a black comet (probably because of the way it's mounted on the base) but I can see why you'd name yours after Don King. Good one!

Jordi - Mary's label matches with mine (I spelled Valadares wrong in my posting). If you say that the locality is incorrect, we have a bit of a mystery... ?

- Tracy

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Jordi Fabre
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PostPosted: Dec 15, 2008 10:06    Post subject: Re: Tracy's favorite specimens (an amateur's adventures)  

Tracy,

I said that I can't be sure about this. I never hear about a mine named Corcunda in Brazil, nor after a search in different well documented sites, but Frank Melanson is a reliable source, so it could be. If I have the chance to speak with him in Tucson I will ask it to him.

Jordi
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