Fraction (mineral)
![](https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Lipari-Obsidienne_%285%29.jpg/220px-Lipari-Obsidienne_%285%29.jpg)
Typical shell-like break in obsidian
The break is a property of minerals and rocks , which is exhibited when as a result of mechanical overloading - for example, shock or pressure - a mineral or rock sample (. Cf. → handpiece ) falls apart along irregularly shaped surfaces.
The appearance of the fracture surfaces, which is often used as a determining criterion, is usually described using the following adjectives:
- shell-like - in amorphous materials and dense aggregates, resembles the imprint of a shell flap (e.g. flint , quartz , glass )
- uneven
- smooth
- fibrous
- hakig - predominantly in solid occurring metals , which viscous be deformed (eg. gold , silver , copper , platinum )
- splintery
- earthy - grainy, irregular fracture surface, similar to weakly solidified sand (e.g. clay minerals )