Alumocalcite

Alumocalcite is an obsolete mineral name historically applied to a hydrated calcium–aluminum carbonate. It is no longer recognized as a distinct species by the International Mineralogical Association (IMA), but appears in older mineralogical literature as a synonym or misidentification.

🌍 Origins and Naming

• Name Origin: From its composition — alumo- (aluminum) + calcite (calcium carbonate).
• Status: Obsolete; modern mineralogy does not treat alumocalcite as a valid species.
• Historical Context: Used in the 19th century to describe earthy, white carbonate-rich material containing both calcium and aluminum.

🔬 Chemical and Structural Properties

• Approximate Composition: Hydrated calcium–aluminum carbonate.
• Related Minerals:
  • Hydrated aluminum carbonates such as dawsonite (NaAlCO₃(OH)₂).
  • Calcium carbonates like calcite (CaCO₃).
• Appearance: White, earthy, clay-like masses.
• Crystal System: Poorly defined; often amorphous or cryptocrystalline.
• Hardness: Soft, clay-like.
• Specific Gravity: Low, reflecting hydration.

⚙️ Geological Occurrence

• Reported from secondary deposits where aluminum-bearing solutions interacted with carbonate rocks.
• Often confused with mixtures of calcite, gibbsite (Al(OH)₃), or other hydrated aluminum phases.
• Rarely identified in modern mineralogical studies due to its instability and mixed composition.

📖 Scientific and Collector Significance

• Petrology: Illustrates early attempts to classify mixed aluminum–calcium carbonates.
• Collectors: Not recognized today; specimens labeled “alumocalcite” are usually reclassified as mixtures or better-defined minerals.
• Modern Status: Considered a discredited name or synonym, with no standing in current mineral taxonomy.

✨ Conclusion

Alumocalcite is an obsolete name for a hydrated calcium–aluminum carbonate, historically described but not recognized today. It represents an early stage in mineral classification, where mixed phases were often given distinct names before structural and chemical analysis clarified their identity.

In short: Alumocalcite = obsolete hydrated Ca–Al carbonate name, now discredited, historically used in 19th-century mineralogy.