biotite
/ˈbaɪətaɪt/
noun
- A dark, shiny mineral found in rocks such as granite, often in thin, flaky sheets.
- The granite countertop sparkled because it contained biotite.
- Geologists identified biotite in the rock sample by its black, glassy flakes.
- Biotite is commonly used to date the age of rocks because it contains potassium.
Synonyms