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Vajdakite
Posted by Rock Currier
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Vajdakite November 10, 2008 07:10PM |
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Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?
Vajdakite
(MoO2)2(H2O)2As23+O5●H2O monoclinic
Czech Republic
The city of Jáchymov (St. Joachimsthal) is located on the southern slope of the, Krušné hory Mountains (Erzgebirge) NW Bohemia, Czech Republic, central Europe. “Vajdakite forms minute acicular crystals or continuous crusts, which form the border of a strongly corroded veinlet. The crystals are translucent and may be easily overlooked. There color varies from gray-green, and aggregates of yellow-green crystals were observed in some cases. Crystals are lath shaped, and their size varies from 0.1 to 0.5 mm. Their termination is highly irregular with needle-like features. Rarely, crystal aggregates cover areas of several square centimeters. Laterally, the vajdakite gives way to gray-green scorodite in spherical and botryoidal aggregates. …Vajdakite is slightly soluble in water. …Vajdakite, one of the rarest secondary minerals at Jáchymov, has been found in only one place-on fractures in proximity to a vein approximately 5 cm thick. Vajdakite occurs with a strongly weathered, intimately intergrown mixture of pyrite, marcasite, nickelskutterduite, löllingite, and native As in the Geschieber vein, on the 12th level of the Svornost shaft. The mixture has partly to completely altered to a mixture of compact, gray-black scorodite (with metallic luster) and arsenolite. Other associated secondary minerals are parascorodite, kaňkiite, annabergite and köttigite. …Vajdakite is formed in an environment of concentrated sulfuric acid, in the presence of As2O3 in significant concentrations.”1
The best specimen was a 4x5 cm with crystals of vajdakite up to 2 mm with a coverage of vajdakite covering about 1x1cm. There were about three such specimens. Crusts of closely packed smaller crystals were more common. The find consisted of about 20 specimens from the size of a thumbnail to about 4x5 cm. The original find was in a tunnel with granite walls and the portion of the tunnel where the vajdakite was found has collapsed and it is very unlikely that more material will be produced.2 The matrix is unstable due perhaps to its acidic nature or moisture in the atmosphere. It tends to crumble. If you have a specimen of this material you should keep it in a well sealed glass bottle. At Jáchymov “Mining of silver ores started in 1516 and the first rich discoveries (the largest recorded piece of native Ag was 280 kg) were followed by a strong silver fever. Jáchymov was rapidly developing and its population reached 18,200 in 1534. Over the centuries, mining of Ag was followed by mining of Co, Ni, Pb, As, and Bi, and later by mining of U and Ra. Mining activities continued with interruptions until 1962 when the last mines were closed.1
1. American Mineralogist., Vol.87, 2002, p983-4.
2. Joseph Vajdak, personal communication 2002.
[Rock Currier 10 November 08]
Click here to view Best Minerals V and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.
Edited 12 time(s). Last edit at 03/26/2012 06:52PM by Rock Currier.
Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?
Vajdakite
(MoO2)2(H2O)2As23+O5●H2O monoclinic
Czech Republic
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| Vajdakite FOV 0.1cm | © 2008, JGW |
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| Vajdakite FOV 0.7mm | © 2008, JGW |
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| Vajdakite FOV 1cm | © Thomas Witzke |
The city of Jáchymov (St. Joachimsthal) is located on the southern slope of the, Krušné hory Mountains (Erzgebirge) NW Bohemia, Czech Republic, central Europe. “Vajdakite forms minute acicular crystals or continuous crusts, which form the border of a strongly corroded veinlet. The crystals are translucent and may be easily overlooked. There color varies from gray-green, and aggregates of yellow-green crystals were observed in some cases. Crystals are lath shaped, and their size varies from 0.1 to 0.5 mm. Their termination is highly irregular with needle-like features. Rarely, crystal aggregates cover areas of several square centimeters. Laterally, the vajdakite gives way to gray-green scorodite in spherical and botryoidal aggregates. …Vajdakite is slightly soluble in water. …Vajdakite, one of the rarest secondary minerals at Jáchymov, has been found in only one place-on fractures in proximity to a vein approximately 5 cm thick. Vajdakite occurs with a strongly weathered, intimately intergrown mixture of pyrite, marcasite, nickelskutterduite, löllingite, and native As in the Geschieber vein, on the 12th level of the Svornost shaft. The mixture has partly to completely altered to a mixture of compact, gray-black scorodite (with metallic luster) and arsenolite. Other associated secondary minerals are parascorodite, kaňkiite, annabergite and köttigite. …Vajdakite is formed in an environment of concentrated sulfuric acid, in the presence of As2O3 in significant concentrations.”1
The best specimen was a 4x5 cm with crystals of vajdakite up to 2 mm with a coverage of vajdakite covering about 1x1cm. There were about three such specimens. Crusts of closely packed smaller crystals were more common. The find consisted of about 20 specimens from the size of a thumbnail to about 4x5 cm. The original find was in a tunnel with granite walls and the portion of the tunnel where the vajdakite was found has collapsed and it is very unlikely that more material will be produced.2 The matrix is unstable due perhaps to its acidic nature or moisture in the atmosphere. It tends to crumble. If you have a specimen of this material you should keep it in a well sealed glass bottle. At Jáchymov “Mining of silver ores started in 1516 and the first rich discoveries (the largest recorded piece of native Ag was 280 kg) were followed by a strong silver fever. Jáchymov was rapidly developing and its population reached 18,200 in 1534. Over the centuries, mining of Ag was followed by mining of Co, Ni, Pb, As, and Bi, and later by mining of U and Ra. Mining activities continued with interruptions until 1962 when the last mines were closed.1
1. American Mineralogist., Vol.87, 2002, p983-4.
2. Joseph Vajdak, personal communication 2002.
[Rock Currier 10 November 08]
Click here to view Best Minerals V and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.
Edited 12 time(s). Last edit at 03/26/2012 06:52PM by Rock Currier.
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Locality Updated: Brancaleone, Reggio Calabria Province, Calabria, ItalyFrom Ferdinando Giovine, 18th May 2013 05:39:48