Alstonite

Alstonite is a rare barium–calcium carbonate mineral, BaCa(CO₃)₂. It is scientifically notable as one of the few double carbonates of barium and calcium, and it occurs in low-temperature hydrothermal veins.

🌍 Origins and Naming

• Name Origin: Named after Alston Moor, Cumbria, England, where it was first discovered.
• Discovery: Described in 1841 by mineralogist Thomas Thomson.
• Type Locality: Alston Moor, Cumbria, England.

🔬 Chemical and Structural Properties

• Formula: BaCa(CO₃)₂
• Mineral Group: Carbonates.
• Crystal System: Trigonal.
• Color: White, colorless, or pale shades (sometimes pinkish or grayish).
• Habit: Tabular crystals, granular aggregates, or massive forms.
• Hardness: ~4–4.5 on Mohs scale.
• Specific Gravity: ~3.7–3.8.
• Luster: Vitreous to pearly.
• Streak: White.

⚙️ Geological Occurrence

• Found in low-temperature hydrothermal veins, often associated with lead–zinc mineralization.
• Associated Minerals: Baryte, calcite, witherite, fluorite, galena, sphalerite.
• Localities:
  • Alston Moor, Cumbria, England (type locality).
  • Other occurrences in Scotland, France, and the USA.

📖 Scientific and Collector Significance

• Petrology: Important for understanding carbonate mineral chemistry, especially Ba–Ca substitutions.
• Collectors: Attractive tabular crystals are rare but valued; more often found as massive aggregates.
• Economic Note: No industrial use; mainly of academic and collector interest.

✨ Conclusion

Alstonite is a rare Ba–Ca carbonate (BaCa(CO₃)₂), first described from Alston Moor, England. It is scientifically significant for illustrating double carbonate chemistry, though it remains a collector’s curiosity rather than an economic resource.

In short: Alstonite = Ba–Ca carbonate, trigonal, rare, first found at Alston Moor, England.