aphanite
/ˈæfənaɪt/
noun
- A fine-grained igneous rock whose individual mineral crystals are too small to be seen with the naked eye.
- Aphanite is often used in construction because its dense, fine texture makes it very durable.
- Under a microscope, the aphanite revealed tiny crystals that were invisible to the naked eye.
- The geologist identified the dark, smooth stone as aphanite because she couldn't see any crystals in it.