Allanite - Hawk-Bakersville, Mitchell County, North Carolina, USA

(A1²⁺REE³⁺)(M1³⁺M2³⁺M3²⁺)O[Si₂O₇][SiO₄](OH)

Allanite - Hawk-Bakersville Area, Mitchell County, North Carolina, USA

Allanite is a rare-earth-element-bearing silicate mineral that is part of the epidote group. The Hawk-Bakersville area in Mitchell County, North Carolina, is a well-known location for allanite specimens, as the region is rich in pegmatitic and metamorphic deposits hosting rare minerals.

Mineralogical Overview

• Chemical Formula: $(Ca,Ce,La,Y)(Al,F{e}^{3+}{)}_3(Si{O}_4{)}_3(OH)$
  • Allanite contains significant amounts of rare earth elements (REEs) such as cerium (Ce), lanthanum (La), and yttrium (Y).
• Mineral Group: Epidote group.
• Appearance:
  • Color: Typically dark brown to black, sometimes with a reddish or greenish tinge.
  • Habit: Found as prismatic to tabular crystals, often elongated, or in granular masses.
  • Luster: Vitreous to resinous.
  • Transparency: Usually opaque, but thin edges may be translucent.

Physical and Optical Properties

• Hardness: 5.5–6 on the Mohs scale.
• Specific Gravity: 3.5–4.2, depending on the REE content.
• Cleavage: Poor to indistinct.
• Radioactivity: Allanite is often mildly radioactive due to its thorium and uranium content.

Geological Context

• Location: The Hawk-Bakersville area in Mitchell County, North Carolina, lies in the Appalachian Mountains, known for its rich pegmatite and metamorphic mineralization.
• Formation: Allanite forms in:
  • Pegmatites: Associated with granitic intrusions rich in rare earth elements.
  • Metamorphic Rocks: Found in high-grade metamorphic environments where REE-bearing fluids interacted with host rocks.
• Associated Minerals:
  • Quartz, feldspar, muscovite, and biotite in pegmatites.
  • Epidote, zircon, monazite, and other REE-bearing minerals.

Significance and Uses

• Collector Interest: Allanite is sought after for its unusual composition and its significance as a rare-earth mineral.
• Geological Importance:
  • Provides insights into rare earth element distribution in pegmatites and metamorphic systems.
  • Indicates REE mobility during geological processes.
• Industrial Use: While not an economic ore, allanite is a minor source of rare earth elements in some cases.

Specimens from Hawk-Bakersville

• Crystal Quality: Allanite from Mitchell County is often well-crystallized, making it desirable for collectors. Crystals are typically dark and contrast nicely with the lighter matrix of quartz or feldspar.
• Size: Crystals range from small, sharp individuals to larger, blocky forms.

Specimen activity on a SE International Ranger EXP: 450 cpm

Approx. size: 100mm x 50mm x 30mm