Research / Geoscience / Language
Anhedral
A mineral grain lacking well-developed external crystal faces, commonly bounded by adjacent grains.
Language and route: English scientific formation from Greek. English anhedral, from Greek ἀν- (an-), ‘not, without’, plus -hedral, ‘faced’
Literal gloss: without (own) faces
The name and its history
First introducer not established · Date not established
- What does the word literally mean?
- The gloss ‘without (own) faces’ describes the linguistic allusion. The original name and its modern scientific definition must be kept distinct.
- What did the original author mean?
- A descriptive shape category for crystals lacking their own external polygonal faces.
- Why was the name needed?
- To describe crystals constrained by neighbours or subsequent growth without mistaking their irregular outline for a species-level mineral property.
- What evidence supported the original concept?
- The absence of clear faces in observed grain sections.
- How has geology changed the concept?
- Modern definitions are descriptive; a two-dimensional thin section may not show the full three-dimensional grain shape.
Further historical context
Anhedral is the opposite of euhedral; subhedral is the intermediate expression.
Related names
Sources
- Geological Survey of India, Rock Texture Atlas — Field and microscopic texture terminology
- IODP proceedings, igneous petrographic methods — Applied petrographic definitions