25 Facts About Alstonite

What is Alstonite?

Alstonite, also known as bromlite, is a rare double carbonate mineral. Its unique properties and complex crystal structure make it a fascinating subject for mineral enthusiasts and scientists alike. Let's dive into some intriguing facts about this mineral.

1. Chemical Composition
   Alstonite's chemical formula is BaCa(CO3)2, meaning it contains barium, calcium, and carbonate ions.

2. Appearance
   Typically colorless to snow-white, alstonite can also appear pale gray, cream, pink, or pale rose-red. Its color may fade when exposed to light.

3. Crystal System
   Alstonite belongs to the triclinic crystal system, which sets it apart from its polymorph paralstonite, which is trigonal.

4. Crystal Structure
   The structure involves layers of barium and calcium ions stacked in a specific arrangement, with carbonate groups located between these layers.

5. Lattice Parameters
   Its lattice parameters are a = 17.38 Å, b = 14.40 Å, c = 6.123 Å, α = 90.35°, β = 90.12°, and γ = 120.08°, with the unit cell containing 24 formula units.

Optical and Physical Properties

Alstonite's optical and physical properties make it a unique mineral. Here are some key aspects:

6. Optical Properties
   Alstonite is biaxial with refractive indices nα = 1.526, nβ = 1.671, and nγ = 1.672. It exhibits weak birefringence and has an optic angle of about 6°.

7. Fluorescence
   Under ultraviolet light, alstonite shows weak yellow fluorescence, both in shortwave and longwave UV light.

8. Solubility
   This mineral is soluble in dilute hydrochloric acid, which can affect its physical properties over time.

9. Hardness
   With a hardness of 4 to 4.5 on the Mohs scale, alstonite is moderately hard.

10. Specific Gravity
    Its specific gravity is around 3.70, slightly above the average density of most minerals.

Cleavage, Fracture, and Twinning

Alstonite's cleavage, fracture, and twinning characteristics contribute to its unique crystal forms.

11. Cleavage
    Alstonite exhibits imperfect cleavage on pseudo-orthorhombic {110} planes, meaning it doesn't cleave easily along these planes.

12. Fracture
    The fracture of alstonite is uneven, indicating it doesn't break cleanly along any particular plane.

13. Twinning
    Commonly exhibits twinning, especially on pseudo-orthorhombic {110} and {310} planes, resulting in complex crystal forms.

Formation and Occurrence

Understanding how and where alstonite forms can provide insights into its rarity and unique properties.

14. Formation
    Alstonite forms through low-temperature hydrothermal processes, where mineral-rich hot water flows through rocks and deposits minerals as it cools.

15. Occurrence
    Found in association with minerals like calcite, barite, and witherite, alstonite is relatively rare.

16. Localities
    Notable localities include Australia, Austria, Brazil, Canada, China, Finland, France, Greenland, India, and Italy.

Historical and Structural Significance

Alstonite has a rich history and a complex structure that has intrigued scientists for years.

17. Historical Significance
    First identified in the mid-19th century, its crystal structure remained unknown until recent studies provided detailed information.

18. Crystal Habit
    Alstonite crystals typically exhibit a steep pseudohexagonal dipyramidal habit, similar to witherite but more acute.

19. Structural Differences
    One main difference between alstonite and paralstonite is the arrangement of cation layers. Alstonite has an ABAB conformation, while paralstonite alternates Ca and Ba atoms along the c-axis.

High-Pressure Studies and Environmental Impact

Recent studies have explored how alstonite behaves under high pressure and its environmental impact.

20. High-Pressure Studies
    High-pressure studies using angle-dispersive powder XRD have provided insights into structural changes under different pressure conditions.

21. Pressure-Induced Changes
    Experiments revealed significant structural changes under pressure, with diffraction patterns showing distinct changes in lattice parameters.

22. Atomic Interaction
    High-pressure experiments allowed for the analysis of atomic interactions, providing valuable information about alstonite's behavior under extreme conditions.

23. Environmental Impact
    Alstonite is not radioactive and poses no known health risks. However, its solubility in dilute HCl indicates it can be affected by acidic environments.

Scientific Interest

Alstonite continues to captivate scientists and mineral enthusiasts due to its unique properties and complex structure.

24. Scientific Interest
    Its complex crystal structure and unique optical properties make alstonite a valuable subject for mineralogical research.

25. Conclusion
    Alstonite remains a fascinating mineral, offering a wealth of information for those interested in mineralogy and crystallography. Its unique properties and complex structure make it an important subject for ongoing scientific study.

Alstonite: A Rare Gem in Mineralogy

Alstonite, also known as bromlite, stands out due to its unique chemical composition and complex crystal structure. This rare double carbonate mineral, composed of barium and calcium, exhibits a range of colors from colorless to pale rose-red. Its triclinic crystal system and biaxial optical properties make it a fascinating subject for scientific study. Found in various locations worldwide, including Australia, Austria, Brazil, and Canada, alstonite forms through low-temperature hydrothermal processes. Its moderate hardness, specific gravity, and weak fluorescence under UV light add to its distinct characteristics. High-pressure studies have revealed significant structural changes, providing insights into atomic interactions. While not radioactive, alstonite's solubility in dilute hydrochloric acid suggests it can be affected by acidic environments. Overall, alstonite's rarity and intriguing properties make it a valuable mineral for ongoing research and mineralogical exploration.