What is an 'inclusion' in a diamond?

What is an 'inclusion' in a diamond?

John Cordova (Vice President of Human Resources, Robbins Bros.) gives expert video advice on: What does a diamond's 'carat weight' mean?; What does a diamond's 'clarity' mean?; What is the diamond clarity grading system? and more...

An inclusion in a diamond is quite simply a natural marking. In some cases, an inclusion can be a cavity in the diamond. It could be another mineral within the diamond. It could be a crack inside the diamond. An inclusion is any mark or blemish in the interior of the diamond.