Habit
Definition
The characteristic external shape of an individual crystal or a group of crystals, such as prismatic, acicular (needle-like), or botryoidal (grape-like).
Example
Quartz often shows a prismatic habit, forming six-sided columns.
The Shape of Things
In mineralogy, "habit" describes the characteristic external shape of an individual crystal or aggregate of crystals. While the internal atomic structure determines the *possible* shapes, the environment determines the *actual* habit. Factors like temperature, pressure, space to grow, and the speed of cooling all influence the final form.
Common Habits
- Prismatic: Elongated, pencil-like crystals (e.g., Tourmaline, Beryl).
- Acicular: Needle-like, very thin crystals (e.g., Rutile).
- Tabular: Flat, tablet-shaped crystals (e.g., Wulfenite, Barite).
- Botryoidal: Grape-like, rounded masses (e.g., Hematite, Malachite).
- Dendritic: Tree-like branching patterns (e.g., Copper, Manganese).
Identifying the habit is a key step in recognizing a mineral specimen in the field.