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.
Peter Robinson under CC-BY-SA licence
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
Geology toolkit
The Open University
Discover the unique landscape of the British Isles with our interactive Geology Toolkit, featuring a geology timeline, rock analyser, rock cycle, landscape features and safety... Read more : Geology toolkit
Be the first to post a comment.
Login or Register to post comments