Group I | Group II | ||
P | Sodalite | 1 | Mottled extinction |
Q | Tourmaline | 2 | Isotropic |
R | Calcite | 3 | Pleochroic from blue to brown |
S | Muscovite | 4 | Twinkling effect |
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 |