Skip to content
Science, Maths & Technology

Microgabbro/ dolerite

Updated Thursday 28th September 2006

A brief description of the nature of microgabbro or dolerite

Microgabbro is a medium-grained intrusive igneous rock. It contains crystals, smaller than rice grains, which are interlocking and randomly oriented. It is dark green to dark grey, with occasional rare paler crystals.

Microgabbro - dolerite Copyrighted image Icon Copyright: The Open University

How is it formed?
Dolerite is the medium-grained equivalent of gabbro. The crystals are slightly smaller than gabbro, indicating that the magma cooled more quickly. It usually occurs as small intrusions called ‘dykes’ or ‘sills’ which are sheet-like and cut through the surrounding rocks.

Like gabbro, dolerite forms from magma that is rich in iron and magnesium, and poor in silica (quartz).

Get closer to geology

 

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

Have a question?

Other content you may like

Microdiorite Creative commons image Icon Peter Robinson under CC-BY-SA licence under Creative-Commons license article icon

Science, Maths & Technology 

Microdiorite

A brief description of the nature of microdiorite

Article
Gabbro Copyrighted image Icon Copyright: The Open University article icon

Science, Maths & Technology 

Gabbro

A brief description of the nature of gabbro

Article
People Like Me: Lorna Copyrighted image Icon Copyright: BBC article icon

Science, Maths & Technology 

People Like Me: Lorna

Who studies science? We talk to students and graduates - and meet Lorna

Article
Amatrice Earthquake: 24th August 2016 - first reactions Creative commons image Icon Paolo Serra under Creative Commons BY-NC-ND 4.0 license video icon

Science, Maths & Technology 

Amatrice Earthquake: 24th August 2016 - first reactions

The OU's Dave Rothery shares what we know so far about this morning's Earthquake in Italy

Video
5 mins
Geology toolkit: landscape features Copyrighted image Icon Copyright: BBC activity icon

Science, Maths & Technology 

Geology toolkit: landscape features

The Geology Toolkit helps explain some of the UK's familiar landscapes

Activity
Mountain building in Scotland Copyrighted image Icon Copyright: Used with permission free course icon Level 3 icon

Science, Maths & Technology 

Mountain building in Scotland

Some of Britain's most dramatic scenery is to be found in the Scottish Highlands. The sight of mighty Ben Nevis, the desolate plateau of the Cairngorms, or the imposing landscapes of Glen Coe can unleash the call of the wild in all of us. Although these landforms were largely carved by glacial activity that ended some 10,000 years ago, the rocks themselves tell of a much older history. The Highlands are merely eroded stumps of a much higher range of ancient mountains. This free course, Mountain building in Scotland, is an account of the origin and demise of that ancient mountain range, based on the geological evidence laid before us in rock exposures.

Free course
30 hrs
Meteorite - or Meteor-wrong? Copyrighted image Icon Copyright: Used with permission article icon

Science, Maths & Technology 

Meteorite - or Meteor-wrong?

There's a simple test which can tell if you've found a rock - or something extra-terrestrial, explains meteorite hunter Rob Elliott

Article
Geological glossary Copyrighted image Icon Copyright: OU article icon

Science, Maths & Technology 

Geological glossary

A glossary of common geological terms.

Article
Sands of time Copyrighted image Icon Copyright: Production team activity icon

Science, Maths & Technology 

Sands of time

Cliffs and fossils can blow away the mystery of the sands of time

Activity