Quartz eyes are a term used to describe rounded and embayed quartz phenocrysts that appear in certain geological contexts.
Understanding Quartz Eyes
Based on research by Betsi and Lentz (2010), quartz eyes are specifically defined as:
- Rounded and Embayed Quartz Phenocrysts: These are individual quartz crystals that are larger than the surrounding rock matrix (phenocrysts) and have irregular, indented margins (embayed), often giving them a somewhat rounded appearance.
These distinctive quartz crystals are typically associated with specific geological processes.
Formation and Occurrence
The presence of quartz eyes is linked to several key processes, suggesting particular conditions under which they form or are modified within the Earth's crust. According to Betsi and Lentz (2010), their occurrence is correlated with:
- Crystallization at high temperatures.
- Crystallization occurring within a magmatic-hydrothermal system, which involves hot, chemically active fluids derived from magma.
- The disaggregation (breaking apart) of earlier-formed bodies rich in quartz.
- The recrystallization of these early quartz-rich bodies.
These processes highlight that quartz eyes are not simply primary crystals but can be the result of complex interactions between magma, fluids, temperature, and existing mineral structures. Their unique rounded and embayed shape provides clues about the geological history and conditions of the rocks in which they are found.
