Abstract
Two varieties of quartz rods (type I and type II) that differ in microstructure and origin occur in graphic granite. Type I rods are pseudomorphous after monoclinic feldspar crystals. These are interpreted to have grown in “negative crystals” that were created during alternation of cellular and tabular gowth phases. Type II rods have irregular qtartz-feldspar interfaces that are located at the extensions of shear faults in the feldspar host. These quartz rods are interpreted as linear dilatational structures generated by interference of regularly spaced shear faults subparallel to crystal cleavages in feldspar. Diagnostic microstructures are parallel opposing surfaces of quartz rods, position of quartz-feldspar interfaces along shear faults, presence of quartz rods in boudin necks ofretrogressive mica, and transitional relationships between graphic granite and cracked, monocrystalline feldspar domains.
