COLUMBITE-(Mn) (formerly Manganocolumbite)
Mica Lode Mine, Eight Mile Park Pegmatite District, Fremont County, Colorado
This well known pegmatite deposit was first written up in the 1940’s by E. William Heinrich of the University of Michigan in Ann Arbor.  For more recent information see “Minerals of Colorado”, by E. B. Eckel, 1997, P. 160 and 359.  All specimens in this group are pure, dark brown-black massive Columbite-(Mn), not the commoner phase Columbite-(Fe).  Compare:
Columbite-(Fe):    Fe²⁺Nb₂O₆
Columbite-(Mn):  (Mn²⁺,Fe²⁺)(Nb,Ta)₂O₆  
While Columbite-(Mn) is generally not a radioactive mineral, the radioactivity present in these specimens is probably due to minor amounts of U or UO₂. Other radioactive minerals identified from this deposit include Uraninite, Parsonsite, and Uranpyrochlore.  Items MI-1835 through MI-1844 are Columbite-(Mn) with very minor, or no associated minerals.  Very thin coatings of pale pink Muscovite can be seen on some specimens.  There is a strong possibility that minor amounts of crystalline, dark brown Uranpyrochlore are present on the backs of specimens MI-1842 and MI-1849, but the associates have not been analyzed.  In the table below, items MI-1845 through 1850, Columbite-(Mn) is associated with small amounts of pale yellow to yellow-tan massive coatings of Parsonsite.   None of the specimens in either group have rock matrix.

1840

1841

1842

1843

1844

PARSONSITE
The following Columbite-(Mn) specimens from the Mica Lode Mine also have very thin massive coatings of secondary, pale yellow to yellow-tan massive Parsonsite present on one or more of the natural surfaces of the Columbite-(Mn).  Parsonsite is: Pb₂UO₂(PO₄)₂.  Not attractive.  None of the specimens have rock matrix.
 

1848

1849

1850

NEW TITLE

“JACHYMOV”,  JOURNAL OF THE CZECH GEOLOGICAL SOCIETY, Edited by Dr. Stanislav Vrana, 11 5/8” X 8 1/4”,  in English, 230 pages, with numerous black & white, as well as color photos, crystal drawings, and SEM’s of the minerals, soft cover.  Your first question is probably…  why would we recommend a book covering such an obscure locality in Czechoslovakia??  Well, read on!  “Jachymov” is the result of years of hard scientific work, and it is the most comprehensive publication about the mines and minerals of the Jachymov Silver and Uranium district ever written.  Jachymov (known as Joachimsthal in old literature) gained world renown through important achievements and discoveries associated with mining and scientific activities during five centuries of exploitation of the ore deposits.  Most recently, the mines at Jachymov were the key producers of the uranium-bearing minerals used by the Russians during the cold war arms race with the USA.  On an historical note, for a part of the 16^th century, Jachymov ranked as the largest Silver producer in the world.  It was the Uraninite from Jachymov on which Maria Sklodowska (Madam Curie) first isolated and discovered two new elements – Polonium and Radium – in 1898.  More than 380 minerals have been identified from Jachymov to date, and the current studies will eventually bring this number up to over 400!  This in-depth report covers the geology of the Jachymov ore district, followed by 137 pages of mineral descriptions with many more than 100 color photos, SEM’s, and crystal drawings.   The next chapter covers the ore-forming processes and mineral parageneses of the Jachymov district.  The chapter on “Who was who in Jachymov mineralogy” presents historical information concerning the discovery of primary minerals first described from Jachymov.  The biographic information about important people after whom the minerals were named goes back to the 17^th century, and includes photographs or portraits of most of these important people. The final chapter covers the history of discovery and study of new primary minerals, and includes photographs of two old labels from mineral specimens recovered in the 1800’s, now in the National Museum of Prague.  Published by the Czech Geological Society, 2003, Prague, Czech Republic.

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