Difference between revisions of "Cleavage"

From The Gemology Project
Jump to: navigation, search
Line 1: Line 1:
{{edit|--[[User:Doos|Doos]] 07:20, 9 December 2006 (PST)}}
+
__forcetoc__
 +
 
 +
==Cleavage==
 +
Cleavage is the splitting of a gemstone along the direction of its crystal faces where molucules have weak bonding. This can occur only in crystalline minerals when a precise blow is given in a particular direction, even if the habit does not show the crystal faces. The result of cleavage is a more or less flat plane with often a silky luster.<br />
 +
 
 +
There are several directions of cleavage.
 +
* Prismatic cleavage
 +
* Basal cleavage
 +
* Pinacoidal cleavage
 +
* Octahedral cleavage
 +
* Rhombohedral cleavage
 +
 
 +
The quality of cleavage is expressed with a few simple phrases.
 +
* Perfect
 +
* Good
 +
* Fair
 +
* Poor
  
 
[[image:cleavage_prismatic.jpg|left|thumb|200px|Prismatic cleavage]]
 
[[image:cleavage_prismatic.jpg|left|thumb|200px|Prismatic cleavage]]
 
[[image:cleavage_basal.jpg|left|thumb|200px|Basal cleavage]]
 
[[image:cleavage_basal.jpg|left|thumb|200px|Basal cleavage]]
 +
<br clear="all" />
 +
 +
==Parting==
 +
 +
Parting is the splitting of a gemstone along twinning planes.
 +
 +
==Fracture==
 +
 +
Fracture is the random breakage of a gemstone when behing hit with a sharp or hard object. The most common type of fracture is termed "conchoidal" (shell-like).<br />
 +
 +
The types of fracture are:
 +
* conchoidal
 +
* uneven
 +
* even

Revision as of 13:49, 9 December 2006


Cleavage

Cleavage is the splitting of a gemstone along the direction of its crystal faces where molucules have weak bonding. This can occur only in crystalline minerals when a precise blow is given in a particular direction, even if the habit does not show the crystal faces. The result of cleavage is a more or less flat plane with often a silky luster.

There are several directions of cleavage.

  • Prismatic cleavage
  • Basal cleavage
  • Pinacoidal cleavage
  • Octahedral cleavage
  • Rhombohedral cleavage

The quality of cleavage is expressed with a few simple phrases.

  • Perfect
  • Good
  • Fair
  • Poor
Prismatic cleavage
Basal cleavage


Parting

Parting is the splitting of a gemstone along twinning planes.

Fracture

Fracture is the random breakage of a gemstone when behing hit with a sharp or hard object. The most common type of fracture is termed "conchoidal" (shell-like).

The types of fracture are:

  • conchoidal
  • uneven
  • even