Definition: Steno's Law, formulated by Nicolaus Steno in 1669, states that the angles between equivalent faces of crystals of the same substance are always constant, regardless of the crystal’s size or whether the crystal is well-formed or distorted.
Explanation
This law is fundamental in crystallography. It implies that the internal arrangement of atoms in a crystal dictates the external geometry, ensuring that the interfacial angles remain consistent. Even if crystals differ in appearance due to growth conditions, the angles between corresponding faces remain identical.
Example
For instance, quartz crystals may vary in size and shape, but the angle between the prism faces remains constant at approximately 120°.
Importance
- Provides evidence of the ordered internal structure of crystals.
- Forms the basis for identifying minerals using crystallographic methods.
- Supports the concept of symmetry in crystallography.