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Mineral composition of the constituting macro units of the Cryolite deposit of Ivigtut

Ivigtut Mine, Ivigtut stock, Arsuk Fjord, Sermersooq, Greenland

Source: H. PAULY & J. BAILEY: Genesis and evolution of the Ivigtut cryolite deposit, SW Greenland, Geoscience 37 (1999)

This entry might provide a helpful context for many of the Ivigut pieces (and discussions) we have on Mindat.

The caption in the source article (table 2) says: “Mineral composition of the units constituting the cryolite deposit. Alteration products of cryolite (thomsenolite, pachnolite, ralstonite and gearkstutite) have been omitted. “ On same page: “Based on mining archives and observations of the authors. ”

Changes done here to the table from the source article:
• For sake of clarity a numbering (1.- 5.) is added here to the units.
• An extra column is added with the estimated total weight of all the minerals (or mineral groups) included in the table. (Multiplying the summary percentage of each row with the estimated total weight, the 12,3 mio tons)
• The layout is changed

The second image loaded here, showing the spatial distribution of the units is directly taken from the same article. I only added (in orange) the mentioned numbering of the five units. For rapid visual linking to the mineral compositions in the table.

The numbering of the units in the table reflects a logical order: That of the sequence in which the units were reached during the mining process. For the first 3 units this is also the order of purity of cryolite – from practically pure cryolite (1.) through siderite-cryolite (2.) to fluorite-cryolite (3.).
By far most of the cryolite volume in the deposit was located in the siderite-cryolite unit. But the outcrop on the surface was a small volume of pure cryolite. These pure cryolite rocks, directly on the seaside, were those sampled by Karl Ludwig Giesecke, who was the first European to visit and report them. It happened already in the very first years of the 19th century, during the Napoleonic wars. And this is where the commercial exploitation begone in 1857.
Around 1900, in the depth of 30 meters near the western wall, a second and much bigger volume of pure cryolite was reached. In 1927 the quarry works arrived to the fluorite (and topaz) containing unit 3.
Units 4. (Fluorite-Topaz) and 5. (Siderite-Quartz) did not contain any cryolite. Hence they were not exploited, and they are still present bellow the ice-cold water that fills the empty quarry.

Units 1-3 no longer exist. They were fully mined, processed in the factory in Copenhagen and used up (mainly) to enable the historical aluminum production of the world.
The physical memory of these geological units are the samples we conserve from them in public and private mineral collections.

Further comments:
a) The amounts stated in the TABLE for the various units are calculated in different ways, which means that the accuracy is not the same.

b) Common Sulfides mean: sphalerite, galenite, chalcopyrite, pyrite. They are always intimately associated with siderite. This fact must be respected in the story of the development of Ivigtut.

c) The strange black cryolite with red-brown fluorite (https://www.mindat.org/photo-1066061.html) is considered in the table as a sub-unit of the Siderite-Cryolite unit.
No trace of Fluorite is found in the Siderite-Cryolite Macro-Unit with the exception of the Fluorite, which is part of this "Black Cryolite With Red-Browne Fluorite".
This fact must also be respected in the story of the development of Ivigtut.

d) The Chiolite is of key importance for understanding the genesis of the Ivigut deposit. The amounts of this mineral in the table should be considered with caution.

GKV-6L4Ordinary chondrite meteorite

Northwest Africa Meteorites

Dimensions: 10 cm x 7 cm x 6 cm
Weight: 840 g

Instructive Imperfections – 7 images of a weathered chondrite meteorite (NWAxxx)

Chondrules are small balls that have given name to this meteorite class. In slices of chondrites we see them as circular structures. To get them exposed, to see them as the small balls they are, we need to look on weathered surfaces. Which is why I am fond of this piece. Due to its somewhat decayed state it shows chondrules in a pedagogical manner.

I interpret its decay history (on Earth) this way:
At its fall this meteorite was much bigger, but it got broken (already at the fall or later). On one side it preserves a curved original surface, that was shaped by the fall. Then the erosion of the piece seems to have happened over relatively long time in a fixed position, part of the piece being buried in soil. I think so because the broken surfaces are of two kind: some are earthy with a nice light ochre color, most probably from the oxidation of the iron flakes inside the chondrite, I suppose because this part was buried in soil. Other parts of the broken surfaces have the typical, bit shiny, dark brown color of chondrites from Sahara; tanned by many many years in the wind.
Finally, to complete the pictures the piece also has a cut surface (without polishing).

In the images I would like to give a spatial sensation of the entire piece and show well the petrological details revealed by the two kinds of decay. Hence, I have played a bit with different positions, lights etc.

The 7 images:
1. (Chondrite lying) Front: original outer surface of the meteorite, that was shaped by the fall. Top/back: broken surface weathered in wind.
2. (Standing) To the right: same original outer surface as on the first image, to the left: broken surface that was weathered buried in soil.
3. Broken surface that was weathered buried in soil - natural light/colour. This nice ochre color is probably due to oxidation of the Fe-Ni flakes in the chondrite.
4. Detail of the previous image (3.) - in artificial light FoV: 3 x 3.5 cm
5. Detail of the broken surface weathered in wind - artificial light FoV: 3 x 3 cm
6. Cut surface - under water, artificial light FoV: 2 x 3 cm
7. Cut surface - dry, natural light/color FoV: 4 x 4 cm

On the cut surface we see chondrules against a good background (in a light matrix) and small shining flakes of metal (iron-nickel).

2DG-HVFCV3 chondrite meteorite, Carbonaceous chondrite meteorite

Northwest Africa Meteorites

Dimensions: 28 mm x 23 mm x 6 mm
Field of View: 30 mm
Weight: 9 g

Carbonaceous Chondrite of CV3 type, from the big deserts of North West Africa. Exact site unknown. (NWAxxx)
(According to the dealer probably found in the area between SE Morocco and SW Algeria)

When acquired, this meteorite weighted 26,6 grams. (in rough state)
I requested a cut in three pieces and polish of some of the faces. (This work was done by a professional in the center of Madrid, who is usually working for gemologists.)

As expected for a CV3 carbonaceous chondrite, the polished surfaces we see here are packed with a variety of different chondrules and CAIs.
* The chondrules are the round/roundish structures, in this piece mostly white, gray and orange.
* CAI is the abbreviation of Calcium Aluminum Inclusions; they are white or pale yellow and exhibit highly irregular, intriguing shapes. (see last pic for drawings of two of them.)
* The third player in this story is the matrix (dust), in which chondrules and CAIs are embedded, containing carbon compounds (hence the name).

The different components (chondrules, CAIs and matrix) are believed to had been formed independently (separately in time and space) and assembled later, on the parent body, from which this meteorite is originated.

Further comments:
CV3 chondrites are believed to have suffered relatively minor transformations only (at least compared to many ordinary chondrites, that can be highly metamorphosed, to the extent that you sometime can hardly even see the chondrules!). Hence CV3s offer one of the best windows to conditions in the early solar system. This is why they are extremely fascinating, and on top they often have an esthetical texture.
The variation between different CV3 chondrites is huge. From an esthetical point of view, I think those with dark matrix (like this one) are more attractive than those with a lighter, gray matrix (as Allende, the most famous CV3).

Images:
1. Slice 1 of 28 x 23 x 6 mm - 9,0 g
2. Slice 2 of 30 x 23 x 5 mm - 6,9 g
3. View of outer surface of the piece, as acquired, before cutting ( 3 x 2 x 1.6cm - 26,6 g )
4. Drawings of two small CAIs from this meteorite
Photos: Canon Power shot, artificial light.

Currently in the meteorite (petrology) collection of Kászon Kovács
***

It is worth noting: The current state of science does not have an “official” (broadly accepted) theory explaining how chondrules and chondrites are formed.
Of course, we have plenty of different theories. If you are interested, this book gives an excellent review:

Derek Sears: The Origin of Chondrules and Chondrites, Cambridge Uni Press, 2004

(you will probably end up with much more questions regarding the subject matter than before opening the book – but this experience will be an enriching and a healthy one.)

9J7-YE4Carbonaceous chondrite meteorite

Northwest Africa Meteorites

Field of View: 3.0 cm

I recently got cut and polished this CV chondrite (NWAxxx), revealing cool details of its petrology. What we see could maybe be tracks of alteration by water on the parent body of this rock. (?)

The cutting exposed an interesting dark gray structure. There are no chondrules inside this region of the piece, and it seems to be considerably softer than the chondrules (as it takes badly the polish). It is penetrated by several small veins of a somewhat harder material. (seems darker because taking better the polish, see on second pic)
Could this structure be interpreted as an agglomeration of the matrix (dust). Due to the movements of water?

Further details about the piece:
*Most of the chondrules are in a degraded state but they are quite diverse, of size and kind. (the size variation seem more pronounced than on my other, more fresh looking CV chondrites)
*A bigger CAI was already visible on the outer surface (see 5th photo). Inside no further bigger CAIs showed up, but several smaller ones, of different forms. All a bit yellowish. (see a very marked CAI on the 3rd photo – more diffuse ones on 4th photo)
*No visible free Fe-Ni metal flakes in the matrix (like usually in CV chondrites), but I see a bit of free metal in association with the chondrules.

Photos:
Pics 1&2: Focuses on the dark gray structure. On each photo we see both sides of the same cut. The two sections are separated by 5 millimeters. (the thickness of the slabs)
Is this structure an agglomeration of matrix (dust) due to water movements on the parent body?
Pics 3&4: Chondrules and CAIs
Pic 5: The piece before being cut, with a bigger CAI visible on the outer surface
(weight before cut & polish: 54g – total weight of all slabs after: 47g)
Pic 6: the end cut, conserving an outer surface (corresponding to the lower side on previous pic)

******
*Piece acquired from: Adrian Contreras (IMCA #7412)
*Cut and polished by: Manuel Baquero Petricorena (who was carefully following my instructions for the orientation of the cuts). We are talking about material difficult to work with, for being so heterogenous and penetrated by cracks. I appreciate the outcome!
*Currently in the meteorite (petrology) collection of: Kászon Kovács
*Photo: Canon Power Shot – natural light around sunset – no filters applied.
******

Example of a reference talking about water impact:
https://www.lpi.usra.edu/meetings/chondrite/pdf/4049.pdf
"Textural Evidence for Asteroidal Alteration: Aqueous alteration within meteorite parent bodies is required by the common occurrence of alteration minerals (…)"

Discussion: https://www.mindat.org/mesg-537281.html

X1D-85UPorphyry

Robledo de Chavela, Community of Madrid, Spain

Dimensions: 6 cm x 5 cm x 4 cm
Field of View: 4 cm

Illustration for my article "Guide to read a Lunar meteorite (NWA11474)":
https://www.mindat.org/article.php/3949/Guide+to+read+a+Lunar+meteorite+%28NWA11474%29

This is a terrestrial rock that could be similar for the superficial sight. A comparison is done in the text.

QY7-99QFeldspathic breccia Lunar meteorite

Mauritania

Dimensions: 35 mm x 25 mm x 1 mm
Weight: 2.5 g

Lunar meteorite (feldspathic breccia) - NWA 11474

Illustration for my article: Guide to read a Lunar meteorite (NWA11474):

https://www.mindat.org/article.php/3949/Guide+to+read+a+Lunar+meteorite+%28NWA11474%29

8UG-4YESchreibersite (Fe,Ni)₃P , Taenite (Fe,Ni) , Iron (Var: Kamacite) (Fe,Ni)

Seymchan meteorite, Srednekansky District, Magadan Oblast, Russia

Dimensions: 5 cm x 4 cm
Weight: 35 g

We have here a relatively big and pedagogical grain of schreibersite in a slice of the Seymchan meteorite. If my understanding is correct this mineral was more abundant on the surface of the Earth before our atmosphere got filled with oxygen. (where phosphides are easily oxidized, hence unstable.) We can talk about a mineral that is extinct from our planetary surface. (There might be a lot of it in the iron core of the Earth, but there it is inaccessible for us)

Seymchan is a pallasite, it also contains big olivine crystals, but not in this slice. (obviously this is “hunted” for the schreibersite grain)
Most of the meteorite is composed of taenite and kamacite, two different iron-nickel alloys. This slice has been treated with nitric acid, which corrodes these two minerals with a slightly different speed, hence revealing the Widmanstätten pattern. (this pattern is different for every iron meteorite, it is a kind of fingerprint.) The Widmanstätten bands in Seymchan are relatively broad.
The schreibersite grain also got somewhat corroded by the acid, but I think this is somehow showing more of the structure of the mineral, hence for me an added value.
The second photo is the flip side of same piece.

2NV-MYFCryolite Na₂NaAlF₆ , Fluorite CaF₂

Ivigtut Mine, Ivigtut stock, Arsuk Fjord, Sermersooq, Greenland

Dimensions: 8.5 cm x 6.0 cm x 3.5 cm
Field of View: 3.5 cm

Red-brown, zoned, thorium containing fluorite crystals in black cryolite. Cut and polished surface.
Of all the strange and exotic mineral assemblages of Ivigtut, for me this is one of the most exciting. To fully appreciate it, its context is needed though, for which I would like to quote Pauly & Bailey, 1999 (full ref in the end):

“An unusual sub-facies of siderite-cryolite, which was totally surrounded by the main facies, was exposed when the bottom of the quarry was about 28 m bellow sea level in 1889. The siderite-cryolite was found to carry cm-sized crystals of zoned red-brown fluorite (…). Due to the presence of about 0,3% Th in this fluorite, the surrounding cryolite was rendered smoky to black by irradiation. In each 5-50 m wide zone of the fluorite the Th content increases outwards, and between the zones there are micron sized minerals rich in REE, Th, Ca and Sr. This material termed ‘black cryolite with red-brown fluorite’, formed a sheet 40 x 30 x 3-5 m in size. (…)” (p 22)
“Although only 1-2 thousand tons of this fluorite are present, it apparently scavenged a high portion of the Th and REE from early “fluids” of the deposit. The amount of Ca removed, however only constitutes about 0,3% of the total Ca in the deposit (…)” (p 35)

Total deposit weighted 12,3 million tons. Of which the cryolite containing rocks (that are now completely removed by mining) constituted total 3,3 million tons. Hence we see that this material was very scarce and localized to one specific spot in the middle of the cryolite deposit.
Also worth noting: the facies in which it is located (called siderite-cryolite in the quoted article) does not contain fluorite except at this spot.
I have owned this piece since the 90ies, but only recently did I send it to cut and polish. I was overwhelmed by the level of details reveled hereby. We clearly see that the cryolite grains are darker in their borders, close to the (slightly) radioactive fluorite crystals. The zonation of the fluorite is also clearly visible in this image. With 40x magnification the mentioned REE containing sulfides between the zones are also visible. (on some spots, not everywhere)
The image also shows quartz and siderite. Outside the field of view I have chosen it also contains the suite of typical Ivigtut sulfides: galena, pyrite and chalcopyrite. Of these three galena is most abundant.

Quoted literature:
PAULY, Hans & BAILEY, John C. : “Genesis and evolution of the Ivigtut cryolite deposit, Southwest Greenland” Geoscience 37. (1999)