Microdiorite

Updated Thursday, 28th September 2006
A brief description of the nature of microdiorite

This page was published 15 years and 3 months ago. Please be aware that due to the passage of time, the information provided on this page may be out of date or otherwise inaccurate, and any views or opinions expressed may no longer be relevant. Some technical elements such as audio-visual and interactive media may no longer work. For more detail, see our Archive and Deletion Policy.

Microdiorite is a medium-grained intrusive igneous rock. It contains crystals that are smaller than grains of rice, which are interlocking and randomly oriented. It is dark grey or greenish brown.

Microdiorite dyke A Microdiorite Dyke in the southeast wall of Kemnay Quarry

How was it formed?
Like diorite, microdiorite forms from magmas that do not contain much quartz (silica) or the light coloured minerals that make up granite. The crystals are smaller than those in Diorite, indicating that the magma cooled more quickly.

It usually occurs as small intrusions called ‘dykes’, which are sheet-like and cut through the surrounding rocks.

 

Get closer to geology

 

 

Author

Author

Ratings & Comments

Share this free course

Copyright information

For further information, take a look at our frequently asked questions which may give you the support you need.

Have a question?