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.)
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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:
- Description: Boltwoodite is a secondary uranium silicate mineral, often forming in the oxidized zones of uranium deposits.
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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:
- Description: Asbolane is a hydrated cobalt-nickel manganese oxide mineral, commonly referred to as "black cobalt" due to its dark color and metallic luster.
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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:
- Description: Birnessite is a layered manganese oxide mineral, commonly occurring as a product of low-temperature chemical weathering.
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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.
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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.
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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







