This specimen is a fantastic “curved” or “bent” quartz crystal. A bent quartz crystal forms where there is significant physical stress on the crystal such that during formation it breaks more or less perpendicular to the c-axis and then continues to grow after slight displacement. When repeated, the process results in continuing growth in a curve. In excellent condition, a couple of small imperfections.
From the Tracy Kimmel collection (with prior labels – Crystal Classics and an unidentified one), a great curved quartz crystal!