Bytownite gabbro
Collection:
Click the microscope button to view a thin section for this sample.
Microscope
Click the microscope button to view a thin section for this sample.
Microscope

Fact sheet

Bytownite gabbro

This coarse-grained igneous rock is a gabbro. The plagioclase-rich plutonic rocks from this locality were once known as eucrites, but that term has been replaced by bytownite gabbro since 'eucrite' is a term now reserved for meteorites thought to originate from the surface of the asteroid Vesta. The rock sample comes from The Cambir in the north west corner of St Kilda, which is an ancient volcano formed in the Paleogene period during the eruption of the North Atlantic volcanic province. The heart of the now eroded volcano is all that is visible above sea level. The island was continuously inhabited for two thousand years until 1930, when the remaining inhabitants of the main island were evacuated to the Scottish mainland. The island is now a world heritage site for natural and cultural study.

In thin section the rock contains strongly cleaved and zoned pyroxene, olivine grains exhibiting cracking and alteration to a combination of chlorite and ilmenite, and bytownite (a calcic plagioclase), which gives the rock its name. 

Additional images
  • Bytownite gabbro  - width 3.3 cm
Map
57.823275, -8.6198
Description:
The Cambir, St Kilda, Scotland
Precision:
Poor
About this collection

The United Kingdom Virtual Microscope (UKVM) collection consists of igneous, sedimentary and metamorphic rocks from around the UK.

It is intended as a teaching resource, helping to tell the story of the common rock types and how they form, and reflecting the history of the UK at the margins of the continent of Europe. The collection is a series of teaching sets, for example igneous rocks from the North Atlantic Igneous Province and SW England; high-temperature metamorphic rocks from Scotland and low-temperature metamorphic rocks from Wales; and sedimentary rocks, including English limestones and sandstones.

Sample details

Type
igneous
Category
gabbro
Rock-forming mineral
olivine
pyroxene
plagioclase
feldspar
Accessory minerals
iron oxide
Category guide  
Category Guide
Title
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Description
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Timescale
Selecting one or more period, for example 'Jurassic'.
Theme
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
Category
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
Owner
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: