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Posted by: Raymond McDougall on 10.23.2018 | Filed under: Latest, Recent Mineral Updates | Comments (0)

This Egypt Update (click here) features excellent goethite pseudomorphs after marcasite from the White Desert, north of Farafra Oasis.

This locality has been known for a number of years and pseudomorph specimens have come out once in a while. The pseudomorphs occur within the Cretaceous Khoman Chalk, from which the White Desert derives its name. Most crystals have typically been fairly indistinct, and to date sharp specimens have been relatively uncommon. These specimens, collected in 2013 and 2014, are remarkable for their relatively sharp marcasite crystal forms in aesthetic crystal clusters.

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 7.0 cm

Over the years, these pseudomorphs have been variously labeled hematite, goethite and limonite (the latter no longer a valid mineral species name, but is a term still used in reference to unidentified iron hydroxides, so its use has not been incorrect). Recent work by Hannah Allen at Hamilton College has confirmed that the White Desert pseudomorphs are predominantly goethite. The small white grains lodged in among the crystal blades are barite, calcite and gypsum. (Allen, Hannah M., Pseudomorphed Mineral Aggregates of the Khoman Chalk, Western Desert, Egypt, Geological Society of America Abstracts with Programs. Vol. 46, No. 2, p.66 (2014)).

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 5.4 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 6.1 cm

Although pseudomorphs after cubic and cuboctahedral pyrite crystals have also been found in the Khoman Chalk, the pseudomorphs after marcasite are more dramatic. These pseudomorphs are excellent specimens featuring beautiful marcasite crystal morphology, showing habits and forms exhibited by the crystallized marcasite specimens from the famous occurrences at Cap-Blanc-Nez, Pas-de-Calais, France.

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.8 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 5.7 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 6.5 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 4.5 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 4.1 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.6 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.8 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.1 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.0 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.0 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt – 3.3 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, Egypt
Same specimen as in the previous photo, bird’s eye view, 2.2 cm across

Posted by: Raymond McDougall on 06.07.2016 | Filed under: Latest, Recent Mineral Updates | Comments (0)

 

I’ve added some great specimens in this Mont Saint-Hilaire Update (click here). One of the world’s great mineral localities, with over 400 species, the quarry has been closed to collecting since 2007 (with isolated exceptions that have not produced specimens in any quantity). The specimens in this update are from finds dated from 1988 to 2007.

One of the most remarkable aspects of collecting at Mont Saint-Hilaire is that no two occurrences are the same – the mineralized zones and pockets are each different, with varied mineral assemblages and crystal habits. This selection of specimens represents several different finds, each of which was unique.

Serandite, Mont Saint-Hilaire, Quebec, Canada

Serandite, Mont Saint-Hilaire, Quebec, Canada – 3.4 cm

Serandite, Mont Saint-Hilaire, Quebec, Canada

Serandite, Mont Saint-Hilaire, Quebec, Canada – 3.4 cm

Serandite, Mont Saint-Hilaire, Quebec, Canada

Serandite, Mont Saint-Hilaire, Quebec, Canada – 3.2 cm

Analcime pseudomorph after analcime, Mont Saint-Hilaire, Quebec, Canada

Analcime pseudomorph after analcime, Mont Saint-Hilaire, Quebec, Canada – 3.7 cm

Manganoneptunite on catapleiite pseudomorph after sodalite, Mont Saint-Hilaire, Quebec, Canada

Manganoneptunite on catapleiite pseudomorph after sodalite, Mont Saint-Hilaire, Quebec, Canada
Field of view 1.0 cm

Rhodochrosite (twinned), Mont Saint-Hilaire, Quebec, Canada

Rhodochrosite (twinned), Mont Saint-Hilaire, Quebec, Canada – 4.5 cm

Analcime on microcline, Mont Saint-Hilaire, Quebec, Canada

Analcime on microcline, Mont Saint-Hilaire, Quebec, Canada – 4.6 cm

Serandite with epidiymite, Mont Saint-Hilaire, Quebec, Canada

Serandite with epididymite, Mont Saint-Hilaire, Quebec, Canada – 7.3 cm

Sodalite, var. hackmanite, pink albite, Mont Saint-Hilaire, Quebec, Canada

Sodalite, var. hackmanite with pink albite coating, Mont Saint-Hilaire, Quebec, Canada – 4.4 cm

Sodalite, var. hackmanite with pink albite coating, Mont Saint-Hilaire, Quebec, Canada

Sodalite, var. hackmanite with albite coating, Mont Saint-Hilaire, Quebec, Canada – 2.5 cm

Narsarsukite, Mont Saint-Hilaire, Quebec, Canada

Narsarsukite, Mont Saint-Hilaire, Quebec, Canada – 1.2 cm crystal

Leucophanite, Mont Saint-Hilaire, Quebec, Canada

Leucophanite, Mont Saint-Hilaire, Quebec, Canada – 2.4 cm

Analcime, Mont Saint-Hilaire, Quebec, Canada

Analcime, Mont Saint-Hilaire, Quebec, Canada – 3.6 cm

Rhodochrosite pseudomorph after serandite, Mont Saint-Hilaire, Quebec, Canada

Rhodochrosite pseudomorph after serandite, Mont Saint-Hilaire, Quebec, Canada – 3.3 cm

Quartz with albite and gaidonnayite, Mont Saint-Hilaire, Quebec, Canada

Quartz with albite and gaidonnayite, Mont Saint-Hilaire, Quebec, Canada – 6.3 cm

Quartz with albite and gaidonnayite, Mont Saint-Hilaire, Quebec, Canada

Quartz with albite and gaidonnayite, Mont Saint-Hilaire, Quebec, Canada – 4.2 cm

Quartz, Mont Saint-Hilaire, Quebec, Canada

Quartz, Mont Saint-Hilaire, Quebec, Canada – 3.2 cm

Elpidite, Mont Saint-Hilaire, Quebec, Canada

Elpidite, Mont Saint-Hilaire, Quebec, Canada – 3.2 cm

Elpidite, Mont Saint-Hilaire, Quebec, Canada

Elpidite, Mont Saint-Hilaire, Quebec, Canada – 4.5 cm

Posted by: Raymond McDougall on 02.28.2016 | Filed under: Latest, Recent Mineral Updates | Comments (0)

I’ve posted some vibrant specimens of chrysocolla pseudomorphs in the new Chrysocolla Update (click here).

Ajoite, Luputo Mine, Lubumbashi, Democratic Republic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo – 8.1 cm

Definitive identification of these specimens has been confirmed. The specimens from this find have been identified as chrysocolla by way of chemical analysis conducted by Dr. Hexiong Yang of the University of Arizona. A preliminary Raman spectroscopic analysis had led to the suggestion of an ajoite identification (which was posted on mindat), but the Raman for each of these minerals is very similar and was therefore inconclusive.

Ajoite, Luputo Mine, Lubumbashi, Democratic Republic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo – 8.7 cm

A couple of observations about these specimens lead me to believe there is some complexity to the formation history. In spots where the underlying pseudomorphs are incomplete, one can examine the cross-sections. Some of those cross-sections reveal that the malachite core is entirely gone (and seems to be chrysocolla), while others retain some malachite. In addition, upon close examination with magnification, one can see there are small malachites sprinkled about, meanwhile the chrysocolla “crystals” have a rather rounded appearance. I believe that the small chrysocolla aggregates themselves are related to the malachite, as pseudomorphs after the malachite. These specimens might in fact be “chrysocolla pseudomorphs after malachite, on chrysocolla pseudomorphs (partial and complete) after malachite pseudomorphs after azurite.” Doesn’t fit on a label so easily, but these are highly unusual and remarkable specimens.

Ajoite, Luputo Mine, Lubumbashi, Democratic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo
Field of view 1.0 cm

These are delicate specimens, with some growths that are thin. As a result, there are incomplete pseudomorphs on almost all I have seen – in fact some are either prominently or mostly without complete ones. These incomplete pseudomorphs actually help to guide our understanding of the specimen’s formation.

Ajoite, Luputo Mine, Lubumbashi, Democratic Republic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo
Field of view 1.0 cm

Ajoite, Luputo Mine, Lubumbashi, Democratic Republic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo – 5.8 cm

Ajoite, Luputo Mine, Lubumbashi, Democratic Republic of the CongoChrysocolla, Luputo Mine, Lubumbashi, Democratic Republic of the Congo
Field of view 1.3 cm

Posted by: Raymond McDougall on 09.23.2015 | Filed under: Latest, Recent Mineral Updates | Comments (0)

 

This Egypt Update (click here) features excellent new goethite pseudomorphs after marcasite crystals from the White Desert, north of Farafra Oasis, Egypt.

This locality has been known for a number of years and pseudomorph specimens have come out once in a while. The pseudomorphs occur within the Cretaceous Khoman Chalk, from which the White Desert derives its name. Most crystals have typically been fairly indistinct, and to date sharp specimens have been uncommon. These new specimens are remarkable for their relatively sharp marcasite crystal forms in aesthetic crystal clusters.

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
5.7 cm

Over the years, these pseudomorphs have been variously labeled hematite, goethite and limonite (the latter no longer a valid mineral species name, but is a term still used in reference to unidentified iron hydroxides, so its use has not been incorrect). Recent work by Hannah Allen at Hamilton College has confirmed that the White Desert pseudomorphs are predominantly goethite. The small white grains lodged in among the crystal blades are barite, calcite and gypsum. (Allen, Hannah M., Pseudomorphed Mineral Aggregates of the Khoman Chalk, Western Desert, Egypt, Geological Society of America Abstracts with Programs. Vol. 46, No. 2, p.66 (2014)).

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
4.7 cm

Although pseudomorphs after cubic and cuboctahedral pyrite crystals have also been found in the Khoman Chalk, the pseudomorphs after marcasite are more dramatic. These pseudomorphs are excellent specimens featuring beautiful marcasite crystal morphology, showing habits and forms exhibited by the crystallized marcasite specimens from the famous occurrences at Cap-Blanc-Nez, Pas-de-Calais, France.

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
3.3 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  Egypt Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
6.5 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
4.4 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
4.2 cm

 Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
4.9 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
4.4 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  Egypt

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
3.6 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
3.6 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
3.0 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
5.4 cm

Goethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate,  EgyptGoethite pseudomorph after marcasite, White Desert, north of Farafra Oasis, New Valley Governorate, Egypt
5.0 cm