- Home
- Rocks
- Type fossils
- Fossil Specimens
- Minerals
- Glossary
- Stratigraphic Chart
- Michel-Levy Chart
- Classification of igneous rocks
- University of Cambridge
- Department of Earth Sciences
- ESC Library
- Moodle
- Sedgwick Museum
- DoITPoMS
- Mindat.org
- Microfossils
- Bryozoans
- Webmineral
- Tree of Life
- CrystalMaker
- Virtual Microscope
Extinction
Title
Extinction
Subject
As a mineral grain is rotated under cross-polarised light it will periodically turn black. When the grain is black it is in extinction. The extinction positions occur at every 90° of rotation. This position is measured in degrees from a prominent feature of the mineral grain, such as a cleavage plane or a face of a euhedral crystal.
Collection
Citation
“Extinction,” 1A Collections, accessed April 9, 2024, https://wserv3.esc.cam.ac.uk/p1acollections/items/show/190.