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Rad Man Minerals

Boltwoodite, Asbolane & Birnessite - Jomac Mine, San Juan, Utah (ex. Patrick Haynes col.)

Boltwoodite, Asbolane & Birnessite - Jomac Mine, San Juan, Utah (ex. Patrick Haynes col.)

Regular price $62.00 USD
Regular price Sale price $62.00 USD
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(K,Na)(UO2)(SiO3OH) · 1.5H2O

(Ni,Co)2-xMn4+(O,OH)4 · nH2O

(Na,Ca)0.5(Mn4+,Mn3+)2O4 · 1.5H2O

Boltwoodite, Asbolane, & Birnessite - Jomac Mine, San Juan County, Utah, USA

The Jomac Mine, located in San Juan County, Utah, is a notable locality for a variety of secondary minerals, particularly those associated with uranium and manganese-rich deposits. Among the minerals of interest from this site are Boltwoodite, Asbolane, and Birnessite, each offering unique geological and mineralogical significance.


1. Boltwoodite

  • Chemical Formula: (K,Na)(UO2)(SiO3OH)1.5H2O
  • Description: Boltwoodite is a secondary uranium silicate mineral, often forming in the oxidized zones of uranium deposits.
  • Appearance:
    • Color: Yellow to orange-yellow.
    • Habit: Fibrous to needle-like crystals, sometimes in radiating aggregates.
    • Luster: Silky to vitreous.
    • Transparency: Transparent to translucent.
  • Formation: Occurs as an alteration product of uraninite or other uranium minerals in the presence of silica and water.
  • Significance: Boltwoodite is a rare mineral prized by collectors. Its bright coloration and crystal habit make it visually distinctive.
  • Handling: As a uranium-bearing mineral, it is radioactive, and precautions must be taken during handling and storage.

2. Asbolane (Asbolite)

  • Chemical Formula: (Co,Ni)2x(Mn,Fe)O4nH2O
  • Description: Asbolane is a hydrated cobalt-nickel manganese oxide mineral, commonly referred to as "black cobalt" due to its dark color and metallic luster.
  • Appearance:
    • Color: Black to dark brown.
    • Habit: Typically found as earthy or massive coatings and crusts.
    • Luster: Submetallic to dull.
    • Transparency: Opaque.
  • Formation: Found in manganese-rich environments, often as a secondary mineral in weathered zones of ore deposits.
  • Significance: Asbolane is a minor ore of cobalt and nickel, with importance in geochemical studies of manganese and cobalt deposits.

3. Birnessite

  • Chemical Formula: (Na,Ca,K)x(Mn4+,Mn3+)2O4nH2O
  • Description: Birnessite is a layered manganese oxide mineral, commonly occurring as a product of low-temperature chemical weathering.
  • Appearance:
    • Color: Black to dark brown.
    • Habit: Found as earthy coatings, films, or fine-grained aggregates.
    • Luster: Dull to earthy.
    • Transparency: Opaque.
  • Formation: Typically forms in oxidized manganese-rich environments, both geologically and biologically mediated.
  • Significance:
    • Plays an important role in geochemical cycling of manganese and other trace elements.
    • Used in studies of environmental remediation due to its ability to adsorb heavy metals.

Geological Context of the Jomac Mine

  • Location: Situated in the uranium-rich regions of San Juan County, Utah, part of the Colorado Plateau.
  • Depositional Environment: The mine is associated with sedimentary-hosted uranium deposits, often linked to vanadium and secondary oxidation products.
  • Associated Minerals:
    • Uraninite: Primary uranium ore.
    • Autunite, Carnotite, Torbernite: Secondary uranium minerals.
    • Pyrolusite and Goethite: Common manganese oxides.
  • Formation: Secondary minerals at the Jomac Mine typically form from the weathering and oxidation of primary ores under arid to semi-arid conditions.

Collecting and Handling

  • Boltwoodite: Requires caution due to its radioactive nature; specimens are often stored in lead-lined containers.
  • Asbolane and Birnessite: Safe to handle but can stain fingers and equipment due to their earthy and powdery nature.
  • Specimen Quality: The Jomac Mine is known for producing aesthetically interesting and mineralogically diverse specimens, making it a favorite among collectors.

Significance

  • The Jomac Mine's minerals provide insights into secondary mineral formation, particularly in uranium and manganese-rich systems.
  • Collectors value specimens from this site for their rarity, beauty, and scientific interest.

 This specimen comes from the collection of noted Geologist Patrick Haynes.

Approx. specimen size: 65mm x 35mm x 10mm

Approx. specimen activity on an SE International Ranger EXP: 2500 cpm

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