Cleavage of Calcitic CaCO₃ during Dissolution in Aqueous Solution

Area of Science:

• Geochemistry
• Materials Science
• Crystallography

Background:

• Calcite (calcium carbonate) is a ubiquitous mineral with significant geological and industrial importance.
• Understanding the formation, dissolution, and cleavage mechanisms of calcite is crucial for various applications, including carbon sequestration and materials engineering.

Purpose of the Study:

• To investigate the accelerated formation and dissolution of calcite in aqueous solutions.
• To characterize the cleavage planes of calcite crystals using advanced electron microscopy techniques.

Main Methods:

• Utilized a device to accelerate calcite formation and dissolution via acidification of aqueous solutions.
• Employed Scanning Electron Microscopy (SEM) for crystal morphology observation.
• Conducted X-ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HR-TEM) for crystallographic analysis and cleavage plane identification.

Main Results:

• Calcite crystals formed within 1 day, with dissolution initiating by day 3.
• X-ray diffraction confirmed predominantly calcite formation, with no amorphous phase detected even after 12 days.
• HR-TEM analysis revealed that calcite cleavage predominantly occurred along the {101̅1} plane, with secondary cleavage observed on the {101̅4} plane.

Conclusions:

• The study successfully demonstrated accelerated calcite formation and dissolution dynamics.
• Identified specific crystallographic planes ({101̅1} and {101̅4}) as primary sites for calcite cleavage.
• Provides fundamental insights into calcite's mechanical behavior and structural properties.