noun
- Plural of greisen; hard, fine-grained metamorphic rocks formed by the alteration of granite, typically containing quartz and mica.
Usage: geology; technical
Examples
- Greisens are commonly found in areas where granite has undergone hydrothermal alteration.
- The mining geologist identified several greisens in the rock samples from the quarry.
- Tin deposits are often associated with greisens formed near granite intrusions.
- These greisens display the characteristic white and gray banding typical of altered granite.