Martha Altobelli

Martha Altobelli

My work seeks to determine the pattern of water concentration as it varies with textural variations within Balmorhea Blue Agate.  This project arose after a summer studying and differentiating between different varieties of agate and what similar characteristics produced the concentric, wall-banded patterns.

My advisor, Dr. Mark Helper, shared my interest in the curiosities of agate.  Previous research models a decreasing water content trend from rim of agate to center.   To test this model, an investigation of the rim to center micro-textural patterns of chalcedonic agate was utilized in comparison with water contents obtained via Fourier Transform Infrared (FTIR) spectroscopy.

The results of transmitted light microscopy, color cathodoluminescent imagery, and FTIR spectroscopy revealed that finely crystalline and chalcedony with higher defect density produced brighter luminosity corresponding with high concentrations of OH-; coarsely crystalline and chalcedony with lower defect density produced weak luminosity and corresponded with low concentrations of OH-.  The calculation of total water content from the rim of agate to center revealed little information compared to specific components of total water, H2Omol and OH-.

Balmorhea Blue Agate

Balmorhea Blue Agate

This study supports the prediction of decreasing water concentration from rim of agate to center, but reveals OH- concentration to vary proportionally with defect density and the inverse of crystal size.

Advisor: Mark Helper