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Jordi Fabre
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Posted: Jan 16, 2010 09:57 Post subject: Naica Mine - (11) |
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Past days grew here one very interesting thread related with Naica -> https://www.mineral-forum.com/message-board/viewtopic.php?t=892 , so maybe is the time to create a thread devoted to this exceptional mining area.
I start it with this classic combo Fluorite & Galena.
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Fluorite with Galena, Arsenopyrite and Calcite Naica mining area, Saucillo, Chihuahua, Mexico Mined about 1980 Specimen size: 7.7 × 5.5 × 4.1 cm. Main crystal size: 3.5 × 2.9 cm. Former Jan Buma collection. Number 020801 Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSBUM-buma-notable-specimens.php#FD29H0 |
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Antonio Alcaide
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Joined: 23 Aug 2009
Posts: 314
Location: Spain
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Posted: Jan 16, 2010 12:23 Post subject: Re: Naica Mine - (11) |
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Here you have my humble contribution.
Regards,
Antonio
Note of the coordinator of the forum:
Locality corrected by petition -> https://www.mineral-forum.com/message-board/viewtopic.php?p=9246#9246
Formerly attributed to Naica.
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Gypsum (Var: Selenite) Laguna del Rey in Coahuila, about 250km east of Naica. 13 x 11 cm (main crystal measuring 10 cm). From my personal collection |
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Peter Megaw
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Joined: 13 Jan 2007
Posts: 963
Location: Tucson, Arizona
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Posted: Jan 16, 2010 12:27 Post subject: Re: Naica Mine - (11) |
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Nice example fo the recent greens with sulfide inclusions from the 520 Level orebody.
Here are some of the collector size gypsums
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Exhibit in mine office with specimens in front of cross section through mine showing multiple chimneys |
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My candidate for the finest gypsum crystal to come out of Naica. This sits in an exhibit case in the mine office and is flawless |
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Peter Megaw
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Joined: 13 Jan 2007
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Location: Tucson, Arizona
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Posted: Jan 16, 2010 12:28 Post subject: Re: Naica Mine - (11) |
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Antonio, nice piece, but it is not from Naica. These distinctive crystals come from Laguna del Rey in Coahuila, about 250km east of Naica.
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Turbo
Joined: 30 Sep 2009
Posts: 260
Location: Delaware
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Posted: Jan 16, 2010 12:34 Post subject: Re: Naica Mine - (11) |
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A Single gypsum crystal with some matrix still attached and showing through from the base. This is one of the thick "parallelogram" type crystals.
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Gypsum var. selenite Naica Mine, Naica, Municipio de Saucillo, Chihuahua, Mexico 14x7x6cm Former Anthony Gricius collection |
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Antonio Alcaide
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Posted: Jan 16, 2010 12:45 Post subject: Re: Naica Mine - (11) |
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Thanks, Peter, for the correction. "Wrong american seller", I'm afraid. I'm going to change my label. I was a bit hesitant because I hadn't found those crystals on Mindat page about Naica (they don't appear on Coahuila page though, but your opinion is beyond all doubt for me).
Regards.
(Please, Jordi, correct the text or erase the post. Thanks a lot).
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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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Posted: Jan 16, 2010 13:35 Post subject: Re: Naica Mine - (11) |
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A nice little cluster of spinel-twin fluorite, acquired at Tucson last year.
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Spinel-twinned fluorite crystals, 3 cm across, Naica. |
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Jordi Fabre
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Location: Barcelona
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Peter Megaw
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Joined: 13 Jan 2007
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Location: Tucson, Arizona
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Posted: Jan 16, 2010 17:42 Post subject: Re: Naica Mine - (11) |
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Jesse...check those fluorite crystals carefully...some have inclusions of curling and curving fibres of an elongate sulfosalt.
Speaking of sulfosalts...here's a cute little bournonite from Naica
and another fluorite
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Bournonite, Naica with calcite and fluorite. These also grow on fluorite. 2 cm. |
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Fluorite, cubic with trisoctahedral modifications with earlier octahedral stage phantom deined by galena crystals. Naica Mine. Scovil photo |
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Peter Megaw
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Joined: 13 Jan 2007
Posts: 963
Location: Tucson, Arizona
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Posted: Jan 16, 2010 17:43 Post subject: Re: Naica Mine - (11) |
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fluorite phantom is 7 cm across a face
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Carles Curto
Joined: 14 Sep 2006
Posts: 160
Location: Barcelona
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Posted: Jan 18, 2010 10:19 Post subject: Re: Naica Mine - (11) |
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Similar to the Fabre's piece, this Fluorite was purchased to Natura Kucera (Barcelona) in 1986, and it was collected few months ago, probably the same year.
Fluorite crystals are slightly beveled by de dodecahedron and Galena crystals are twinned (spinel twin)
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Fluorite Gibraltar Mine, Naica, México. 5,5 x 6,8 x 4,9 cm main crystal 3,7 x 3,7 x 4,1 cm |
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Jordi Fabre
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Posted: Jan 20, 2010 10:15 Post subject: Re: Naica Mine - (11) |
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A cute Gypsum from upper oxide levels of Naica Mine.
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Gypsum Upper oxide levels, Naica Mine, Naica, Municipio de Saucillo, Chihuahua, Mexico Crystal size: 15 x 2 cm. Former James Catmur collection Photo: Joan Rosell |
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The same crystal standing up |
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John S. White
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Joined: 04 Sep 2006
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Location: Stewartstown, Pennsylvania, USA
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Posted: Jan 20, 2010 14:03 Post subject: Re: Naica Mine - (11) |
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Thank you Jordi for calling this gypsum and not selenite.
_________________ John S. White
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Jordi Fabre
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Posted: Jan 20, 2010 14:12 Post subject: Re: Naica Mine - (11) |
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Gypsum is what it is, Master. ;-)
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Peter Megaw
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Location: Tucson, Arizona
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Posted: Jan 21, 2010 02:34 Post subject: Re: Naica Mine - (11) |
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Yes, grasshopper, but it is the Naica Mine...not the Gibraltar
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Jordi Fabre
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Posted: Jan 21, 2010 03:23 Post subject: Re: Naica Mine - (11) |
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OK Master 2.
Anyway, I have a doubt. In https://www.mineral-forum.com/message-board/viewtopic.php?p=9227#9227 you said:
Peter Megaw wrote: | Gibraltar was operated by Eagle Picher Mining until it was purchased by the Fresnillo Mining Company (now Penoles...which spun off the new Fresnillo pls in 2008) in 1955. The Gibraltar name survives as the name of one of the two hoisting shafts, the upper part of which used to service what was the Gibraltar Mine. However, it is inaccurate to call it the Gibraltar Mine. Penoles, has used the Naica name since they acquired and consolidated the district in 1955 and began sulfide production. ALL specimens from the sulfide zone should be labeled Naica Mine. |
and this Gypsum is quite old, so it could been mined in the former Gibraltar mine? and if yes, what is adequate, the name that the mine had when the specimen was mined or the current's mine name? ;-)
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Peter Megaw
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Location: Tucson, Arizona
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Posted: Jan 21, 2010 10:01 Post subject: Re: Naica Mine - (11) |
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It is possible since the entire mountain seems to be riddled with gypsum pockets...but the Cave of the Swords and sister cavern where most of the historic gypsum specimens came in quantity from were in the Maravilla and Lepanto workings. I used to buy crystals by the carload from the mine manager...they harvested them from the Cave of the Swords, sold them and used th proceeds to pay for the refreshmensts served in the miner's club.
Unless you have some reason to think whoever made the label that goes with this piece really knew which mine it came from, you would probably be safest to put "upper oxide levels" "Naica Mine" on the label, perhaps noting a pre-1955 harvest date.
The mine is almost equally well endowed with anhydrite crystals, they are everywhere... except they don't choke up the pumping system and sumps or line enormous caverns. There has been a fair amount of work done on the origin/source of the gypsum and anhydrite...Google "Naica" and "Geology" and you will be led to the April 2007 article in the scientific journal "Geology" on the subject. Although it does have some significant flaws regarding crystal growth, it shows the that both the gypsum and anhydrite are derived from evaporite beds that occur in the host rock section below the principal limestone units. Both the limestone and anhydrite/avaporite beds at that depth are thoroughly thermally metamorphosed to coarse-grained marble...if that term can be applied to the evaporites. The ore fuids passing through dissolved the "primary" anhydrite and it reprecipitated as anhydrite with sulfides in the orebodies or gypsum on sulfides depending on the temperature. Interestingly the "secondary" anhydrite crystals we see from the mine are sky-blue to grayish blue in color whereas the bedded anhydrite at depth is lilac in color.
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Anhydrite crystal 12 cm long. Naica Mine |
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Giant gypsum crystal from Naica Mine |
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Jordi Fabre
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Gerhard Niklasch
Joined: 27 Mar 2009
Posts: 134
Location: Munich
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Posted: Apr 18, 2010 16:32 Post subject: Re: Naica Mine - (11) |
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A while ago, Peter Megaw wrote: | Jesse...check those fluorite crystals carefully... some have inclusions of curling and curving fibres of an elongate sulfosalt.
(...)
Fluorite, cubic with trisoctahedral modifications with earlier octahedral stage phantom defined by galena crystals.
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Here's a Naica fluorite miniature (I had once shown it to Jordi in person) exhibiting all of these traits, as well as some nice calcite / chalcopyrite / sphalerite decorations on the matrix. Acquired by yours truly in October 2009, collection id 09MXFSCc3.
The overall specimen dimensions are 47x42x31mm.
The cube {100} and dodecahedron {110} faces are perfectly smooth, the other faces are frosted.
Stereo photos are in crossed-eyes mode.
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The shape and orientation of the bright {110} face provide the easiest way to deduce that the surrounding faces are {113}. {112} would give the same diamond shape with angles of 70.5° and 109.5° but oriented the other way, acute corners towards the cube face. {114} and higher forms would cut narrower rhombs out of the {110} face. |
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Side view (taken through the microscope), faces labelled with their Miller indices. Field of view 15x11.5mm. |
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Same in stereo. The octahedral {111} faces are very small. FOV 9x16.7mm. |
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Stereo view onto the top of the specimen. The interior is very pale green and perfectly transparent. (Note that the cube(001) face is "standing on end" as it were, its edges at 45° to the axes.) |
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Close-up looking at the inclusions - as far as I can tell, there's both galena (the lustrous octahedra) and sphalerite (the rougher shapeless grains) among them. At this magnification (FOV 10.9x18.1mm), it becomes obvious that they sit on an otherwise almost invisible interior phantom which is mostly octahedral, except the corner pointing towards us is truncated by a small cube face, oriented the same way as the one through which we're looking. |
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Magnifying even more (FOV 4.3x5.7mm) and looking at one edge of the phantom, whose apex is near the top right corner of the frame, we see that the galena/sphalerite grains rest just on the outside of the phantom shape, while small fibers of metallic luster sit just below the phantom surface. The outer top face of the Fluorite through which we're looking is almost invisible now! If you look around a bit, you may discover one or two small blemishes on it showing up as bright dots, e.g. one near the lower right-hand edge of this frame. |
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And one more at high mag (FOV 4.65x5.9mm), looking at the truncated apex of the interior phantom octahedron (a little below and to the right of the center of the frame). |
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Pete Richards
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Posted: Apr 19, 2010 15:53 Post subject: Re: Naica Mine - (11) |
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Very often modifying faces on fluorite are misidentified. The usual confusion, when modifying faces of a cube occur in groups of three, is whether the faces belong to a trisoctahedron or a trapezohedron. Since the faces meet at a corner of the cube, where an octahedron would be if it were present, folks often think these faces belong to a trisoctahedron - the thinking being "trisoctahedron" - "three-octahedron" - "three [faces instead of an ] octahedron [face]". In my experience, these modifying faces usually belong to a trapezohedron, {311} being the most common. The Naica Mine fluorites are more complex, and I think Herr Niklasch is right in his analysis. But as a general rule, if the modifying faces appear primarily to cut off the edges of the cube, they belong to a trisoctahedron. If they appear primarily to cut off the faces, they belong to a trapezohedron. In either case, they modify the corner, with three faces replacing one hypothetical faces of an octahedron!
Trapezohedra have the general Miller indices {hkk}, where h is greater than k, e.g. {211}. Trisoctahedra have the general indices {hhk}, where h is greater than k, e.g. {221}. Since all three axes are equivalent in the isometric system, {211} can equally validly be written as {121} or {112}, where the curly brackets mean that the Miller indices represent all faces of the form, not just one face. {211} and {112} are common choices in different regions of the world; I think {121} is rarely if ever used when all three choices are equivalent.
Attached are a couple of drawings.
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_________________ Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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