Extinction

Question 1

Parallel Extinction

Answer 1

Hexagonal, Tetragonal, Orthorhombic

Question 2

Inclined Extinction

Answer 2

Monoclinic, Triclinic

Question 3

Gives mineral a pebbly appearance as passes to extinction.

Answer 3

Bird’s eye extinction

Question 4

Hexagonal System (Includes trigonal minerals)

• Quartz (β-Quartz at high temperatures)
• Apatite
• Beryl
• Graphite
• Corundum
• Tourmaline
• Calcite (Rhombohedral, but can appear hexagonal in some sections)
• Dolomite

Answer 4

Parallel

Question 5

Tetragonal System

• Zircon
• Rutile
• Cassiterite
• Anatase
• Scheelite
• Vesuvianite (Idocrase)

Answer 5

Parallel

Question 6

Orthorhombic System

• Olivine (Forsterite-Fayalite Series)
• Andalusite
• Kyanite
• Sillimanite
• Topaz
• Barite
• Enstatite (Orthopyroxene group)
• Hypersthene (Orthopyroxene group)
• Staurolite
• Chrysoberyl

Answer 6

Parallel

Question 7

• Augite (Clinopyroxene group)
• Diopside (Clinopyroxene group)
• Hornblende (Amphibole group)
• Actinolite (Amphibole group)
• Tremolite (Amphibole group)
• Glaucophane (Amphibole group)
• Epidote
• Titanite (Sphene)
• Serpentine
• Micas (Biotite, Muscovite, Phlogopite, Lepidolite)
• Orthoclase (Potassium Feldspar, sometimes Carlsbad twinning is visible)
• Chlorite (Can also show anomalous colors)

Answer 7

Inclined

Question 8

Triclinic System

• Plagioclase Feldspars (Albite, Labradorite, Anorthite, Oligoclase, Andesine, Bytownite)
• Microcline (Potassium Feldspar, shows characteristic cross-hatch twinning)
• Axinite
• Rhodonite
• Kyanite (Sometimes inclined, depending on orientation)

Answer 8

Inclined