In crystallography, a ”dome” is a crystal form that typically consists of two non-parallel faces related by a mirror plane. This description matches option (D), where the two non-parallel faces are symmetrically related by a mirror plane. The other options describe different symmetry relationships
Group I | Group II |
P. Sillimanite | 1. First order |
Q. Quartz | 2. Second order |
R. Muscovite | 3. Greater than third order |
S. Calcite | 4. Third order variegated |