Rhombohedral vs. Prism Sector Zones in Hydrothermal Quartz Crystals : Implications for Growth Dynamics

Abstract

Gemmy hydrothermal quartz crystals typically exhibit each of their six prism and six rhombohedral crystal faces. However, discerning which of the crystal faces were actively growing at any given time during construction of an individual crystal has been problematic. Recently, we have shown that hydroxyl-bearing impurities are readily incorporated into active rhombohedral growth faces, but not so in active prism growth faces. Infrared spectroscopic measurements reveal that distinct sector zones with unique impurity concentrations identify the active growth faces responsible for growth of each sector zone. However, it is still not known whether activity on a growth face reflects conditions reflective of the external environment or internal to the crystal lattice. Here, we use infrared spectroscopy and polarized light microscopy to characterize the evolving sector zones within a series of quartz crystals that grew at the same time inside a single vug. In a preliminary set of measurements on three crystals, we observe that thick prism sector zones correlate with proximity to the fracture wall and may reflect that flow dynamics within the host hydrothermal fluid connect with growth activity on prism walls. Here, we further explore this intriguing correlation.